
































. 




Glass 
Book. 



4 1 



< 



JUST PUBLISHED, IN ONE VOLUME, 8VO. 

MATHEMATICS FOR PRACTICAL MEN; 

BEING 

A COMMON PLACE BOOK 

OF 

PRINCIPLES, THEOREMS, RULES AND TABLES, IN VARIOUS DEPARTMENTS 

OF 

PURE AND MIXED MATHEMATICS, 

With their applications ; especially to the pursuits of Surveyors, Architects, 
Mechanics, and Civil Engineers. With numerous engravings. 

BY OLINTHUS GREGORY, LL. D., F. R. A. S. 

" Only let men awake, and fix their eyes, one while on the nature of things, another 
while on the application of them to the use and service of mankind." — Lord Bacon. 

SECOND EDITION, CORRECTED AND IMPROVED. 

Extract of a Letter from Walter R. Johnson, .Professor of Mechanics 
and Natural Philosophy in the Franklin Institute. 

" This treatise is intended and admirably calculated to supply the defi- 
ciency in the means of mathematical instruction to those who have neither 
time nor inclination to peruse numerous abstract treatises in the same de- 
partments. It has, besides the claims of a good elementary manual, the 
merit of embracing several of the most interesting and important depart- 
ments of Mechanics, applying to these the rules and principles embraced in 
the earlier sections of the work. 

" Questions in Statics, Dynamics, Hydrostatics, Hydrodynamics, &c, are 
treated with a clearness and precision which must increase the powers of 
the student over his own intellectual resources by the methodical habits 
which a perusal of such works cannot fail to impart. 

" With respect to Engineering, and the various incidents of that impor- 
tant profession, much valuable matter is contained in this volume ; and the 
results of many laborious series of experiments are presented with concise- 
ness and accuracy." 

Letter from Albert B. Dod, Professor of Mathematics in the College of 

New Jersey. 
" Messrs. Carey & Hart, 

" Gentlemen, — I am glad to learn that you have published an American 
edition of Dr. Gregory's ' Mathematics for Practical Men.' I have for 
some time been acquainted with this work, and I esteem it highly. It con- 
tains the best digest, within my knowledge, of such scientific facts and prin- 
ciples, involved in the subjects of which it treats, as are susceptible of direct 
practical application. While it avoids such details of investigation and pro- 
cesses of mathematical reasoning as would render it unintelligible to the 
general reader, it equally avoids the sacrifice of precision in its statement 



MATHEMATICS FOR PRACTICAL MEN.- 

of scientific results, which is too often made in popular treatises upon the 
Mathematics and Natural Philosophy. ■ The author has succeeded to a re- 
markable degree in collecting such truths as will be found generally useful, 
and in presenting them, in an available form, to the practical mechanic. To 
such, the work cannot be too strongly recommended ; and to the student, too, 
it will often be found highly useful as a book of reference. 
" With much respect, 

" Your obedient servant, 

"ALBERT B. DOD, 
" Professor of Mathematics in the College of New Jersey. 
"Princeton, Nov. 11, 1834." 

Extract of a Letter from Edward H. Courtenay, Professor of Mathe- 
matics in the University of Pennsylvania, 

"The design of the author — that of furnishing a valuable collection of 
rules and theorems for the use of such as are unable, from the want of time 
and previous preparation, to investigate mathematical principles — appears to 
have been very successfully attained in the present volume. The informa- 
tion which it affords in various branches of the pure and mixed Mathematics 
embraces a great variety of subjects, is arranged conveniently, and is in 
general conveyed in accurate and concise terms. To THE ENGINEER, 
THE ARCHITECT, THE MECHANIC— indeed to all for whom results 
are chiefly necessary — the work will doubtless form a very valuable acqui- 
sition." 

Letter from Charles Davies, Professor of Mathematics in the Military 
Jlcaderny, West Point. 

" Military Academy, West Point, May 14th, 1835. 
" To Messrs. E. L. Carey Sf A. Hart, — 

"The 'Mathematics for Practical Men,' by Dr. Gregory, which you have 
recently published, is a work that cannot fail to be extensively useful. 

"It embraces, within a comparatively small compass, all the rules and for- 
mulas for mathematical computation, and all the practical results of mecha- 
nical philosophy. It is, indeed, a collection of the useful results of science 
and the interesting facts which have been developed by experience. It may 
safely be said, that no work, of the same extent, contains so much informa- 
tion, with the rules for applying it to practical purposes. 
"I have the honour to be, 

" With great respect, 

" Your obedient servant, 

"CHARLES DAVIES, 

" Professor of Mathematics." 

Extract from a Letter from J. A. Miller, Professor of Mathematics in 
Mount St. Mary's College, Emmettsburg, Md. 

" Since the London edition of Gregory's Mathematics for Practical Men 
appeared in this country, it has been much used in this institution. The 
accuracy of its definitions, its beautiful systematic arrangement, the many 
simplified and facilitated methods which it proposes, and its highly practical 
character, must recommend it strongly to public patronage, as one of the 
very best works which have lately issued from the press. I have examined 
your edition of this valuable work sufficiently to say with confidence that it 
is very accurately printed." 



: !, .\rr uii&m-irauESSTUiBUB TEreiEnE 



PI. XIII. 



;■/, ty/,>t,/,r. :>'-, /;■<■/ xtw/<,-. 




Jiii./r. fy J: JCiv 



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THE 

STEAM ENGINE 

FAMILIARLY EXPLAINED AND ILLUSTRATED; 



AN HISTORICAL SKETCH OF ITS INVENTION AND 
PROGRESSIVE IMPROVEMENT ; 



ITS APPLICATIONS TO 



NAVIGATION AND RAILWAYS, 



PLAIN MAXIMS FOR RAILWAY SPECULATORS. 

BV THE 

REV. DIONYSIUS LARDNER, LL.D., P.R.S., 

FELLOW OF THE ROYAL SOCIETI OF EDINBURGH J OF THE ROYAL IRISH ACADEMY , 

OF THE ROYAL ASTRONOMICAL SOCIETY J OF THE CAMBRIDGE 

PHILOSOPHICAL SOCIETY ; OF THE STATISTICAL SOCIETY OF PARIS ; OF THE 

LINNjEAN AND ZOOLOGICAL SOCIETIES J OF THE SOCIETY FOR 

PROMOTING USEFUL ARTS IN SCOTLAND, ETC. 

WITH ADDITIONS AND NOTES, 

BY JAMES RENWICK, LL. D., 

PROFESSOR OF NATURAL EXPERIMENTAL PHILOSOPHY AND CHEMISTRY 
IN COLUMBIA COLLEGE, NEW YORK. 

ILLUSTRATED BY ENGRAVINGS AND WOODCUTS. 



SECOND AMERICAN, PROM THE FIFTH LONDON, EDITION, 
CONSIDERABLY ENLARGED. 



PHILADELPHIA : 

E. L. CAREY & A. HART 
1836 






IStltfVtU, according to the Act of Congress, in the year 1836, by 
E. L. Carey & A. Hart, in the Clerk's office of the District Court for 
the Eastern District of Pennsylvania. 



J2//0 






1 

: i 
I 



PREFACE 



THE AMERICAN EDITOR 



Several of the additions, which were made by the Editor 
to the first American edition, have been superseded by the 
great extension, which the original has from time to time 
received from its author. This is more particularly the 
case, with the sections which had reference to the character 
of steam at temperatures other than that of boiling water, to 
the use of steam in navigation, and to its application to loco- 
motion. These sections have of course been omitted. A 
few new sections, and several notes have been added, illus- 
trative of such points as may be most interesting to the 
American reader. 

Columbia College, 
New York, March, 1836- 



PREFACE 



THE FIFTH EDITION 



This volume should more properly be called a new work 
than a new edition of the former one. In fact the book has 
been almost rewritten. The change which has taken place, 
even in the short period which has elapsed since the publi- 
cation of the first edition, in the relation of the steam engine 
to the useful arts, has been so considerable as to render this 
inevitable. 

The great extension of railroads, and the increasing num- 
ber of projects which have been brought forward for new 
lines connecting various points of the kingdom, as well as 
the extension of steam navigation, not only through the seas 
and channels surrounding and intersecting these islands, and 
throughout other parts of Europe, but through the larger 
waters which are interposed between our dominions in the 
East and the countries of Egypt and Syria, have conferred 
so much interest on the application of steam to transport, 
that 1 have thought it adviseable to extend the limits of the 
present edition considerably beyond those of the last The 
chapter on railroads has been enlarged and improved. Three 



Vlll PREFACE. 



chapters have been added. The twefth chapter contains a 
view of steam navigation; the thirteenth contains several im- 
portant points connected with the economy of steam power, 
which, when this work was first published, would not have 
offered sufficient interest to justify their admission into a 
popular treatise ; and the fourteenth chapter contains a series 
of compendious maxims, for the instruction and guidance of 
persons desirous of making investments or speculating in 
railway property. 

London, December, 1835. 



PREFACE 



THE FIRST EDITION 



There are two classes of persons whose attention may be 
attracted by a treatise on such a subject as the Steam Engine. 
One consists of those who, by trade or profession, are inte- 
rested in mechanical science, and who therefore seek infor- 
mation on the subject of which it treats, as a matter of 
necessity, and a wish to acquire it in a manner and to an 
extent which may be practically available in their avocations. 
The other and more numerous class is that part of the public 
in general, wKo, impelled by choice rather than necessity, 
think the interest of the subject itself, and the pleasure' de- 
rivable from the instances of ingenuity which it unfolds, 
motives sufficiently strong to induce them to undertake the 
study of it. Without leaving the former class altogether 
out of view, it is for the use of the latter principally that the 
following lectures are designed. 

To this class of readers the Steam Engine is a subject 
which, if properly treated of, must present strong and pecu- 

2 



X PREFACE. 

liar attractions. Whether we consider the history of its 
invention as to time and place, the effects which it has pro- 
duced, or the means by which it has caused these effects, we 
find everything to gratify our national pride, stimulate our 
curiosity, excite our wonder, and command our admiration. 
The invention and progressive improvement of this extraor- 
dinary machine, is the work of our own time and our own 
country; it has been produced and brought to perfection 
almost within the last centur}', and is the exclusive offspring 
of British genius fostered and supported by British capital. 
To enumerate the effects of this invention, would be to count 
every comfort and luxury of life. It has increased the sum 
of human happiness, not only by calling new pleasures into 
existence, but by so cheapening former enjoyments as to 
render them attainable by those who before never could have 
hoped to share them. Nor are its effects confined to England 
alone: they extend over the whole civilized world; and the 
savage tribes of America, Asia, and Africa, must ere long 
feel the benefits, remote or immediate, of this all-powerful 
agent. 

If the effect which this machine has had on commerce and 
the wealth of rations raise our astonishment, the means by 
which this effect has been produced will not less excite our 
admiration. The history of the Steam Engine presents a 
series of contrivances, which, for exquisite and refined inge- 
nuity, stand without a parallel in the annals of human inven- 
tion. These admirable contrivances, unlike other results of 
scientific investigation, have also this peculiarity, that to 
understand and appreciate their excellence recpuires little 
previous or subsidiary knowledge. A simple and clear ex- 



PitEFACE. xi 

planation, divested as far as possible of technicalities, and 
assisted by well selected diagrams, is all that is necessary to 
render the principles of the construction and operation of 
the Steam Engine intelligible to a person of plain under- 
standing and moderate information. 

The purpose for which this volume is designed, as 
already explained, has rendered necessary the omission of 
many particulars which, however interesting and instructive 
to the practical mechanic or professional engineer, would 
have little attraction for the general reader. Our readers 
require to be informed of the general principles of the con- 
struction and operation of Steam Engines, rather than of 
their practical details. For the same reasons we have con- 
fined ourselves to the more striking and important circum- 
stances in the history of the invention and progressive im- 
provement of this machine, excluding many petty disputes 
which arose from time to time respecting the rights of 
invention, the interest of which is buried in the graves of 
their respective claimants. 

In the descriptive parts of the work we have been govern- 
ed by the same considerations. The application of the force 
of steam to mechanical purposes has been proposed on vari- 
ous occasions, in various countries, and under a great variety 
of forms. The list of British patents alone would furnish 
an author of common industry and application with matter 
to swell his book to many times the bulk of this volume. 
By far the greater number of these projects have, however, 
proved abortive. Descriptions of such unsuccessful, though 
frequently ingenious machines, we have thought it adviseable 
to exclude from our pages, as not possessing sufficient in- 



XI! PREFACE. 

terest for the readers to whose use this volume is dedicated. 
We have therefore strictly confined our descriptions either 
to those Steam Engines which have come into general use, 
or to those which form an important link in the chain of 
invention. 

December 36, 1827. 



CONTENTS, 



CHAPTER I. 



PKELIMINARlf MATTER. 



Motion the Agent in Manufactures.-r-Animal Power. — Power depending 
on physical Phenomena. — Purpose of a Machine. — Prime Mover. — Me. 
chanical qualities of the Atmosphere. — Its Weight. — The Barometer. 
— Fluid Pressure. — Pressure of rarefied Air. — Elasticity of Air. — 
Bellows. — Effects of Heat. — Thermometer. — Method of making one. 
— Freezing and Boiling Points. — Degrees. — Dilatation of bodies. — 
Liquefaction and Solidification. — Vaporisation and Condensation. — 
Latent Heat of Steam. — Expansion of Water in Evaporating. — Effects 
of Repulsion and Cohesion. — Effect of Pressure upon Boiling Point. — 
Formation of a Vacuum by Condensation. Page 17 

CHAPTER II. 

FIRST STEPS IN THE INVENTION, 

Futility of early Claims.^- Watt the real Inventor. — Hero of Alexandria, 
— Blasco Garay. — Solomon De Caus. — Giovanni Branca. — Marquis 
of Worcester.— Sir Samuel Morland. — Denis Papin. — Thomas Sa. 
very. 38 

CHAPTER HI. 

ENGINES OF SAVERY AND NEWCOMEN. 

Savery's Engine. — Boilers and their Appendages. — Working Apparatus. 
— Mode of Operation. — Defects of the Engine. — Newcomen and Caw- 
ley. — Atmospheric Engine. — Accidental discovery of Condensation 
by Jet. — Potter's discovery of the Method of working the Valves, 

51 



XIV CONTENTS. 



CHAPTER IV. 

ENGINE OF JAMES WATT. 



Advantages of the Atmospheric Engine over that of Captain Savery. — 
It contained no new Principle. — Papin's Engine. — James Watt. — Par- 
ticulars of his Life. — His first conceptions of the Means of economising 
Heat. — Principle of his projected Improvements. Page 69 

CHAPTER V. 

■watt's SINGLE-ACTING steam engine. 

Expansive Principle applied. — Failure of Roebuck, and partnership with 
Bolton. — Patent extended to 1800. — Counter. — Difficulties in getting 
the Engines into Use. 80 

CHAPTER VI. 

DOUBLE-ACTING STEAM ENGINE. 

The Single-acting Engine unfit to impel Machinery. — Various Contri- 
vances to adapt it to this Purpose. — Double-Cylinder.— Double-acting 
Cylinder.— Various modes of connecting the Piston with the Beam. — 
Rack and Sector. — Double Chain. — Parallel Motion. — Crank. — Sun 
and Planet Motion. — Fly Wheel— Governor. 91 

CHAPTER VII. 

DOUBLE-ACTING STEAM ENGINE, 

continued. 

On the Valves of the Double-acting Steam Engine. — Original Valves. — 
Spindle Valves. — Sliding Valve. — D Valve. — Four-Way Cock. 108 

CHAPTER VIII. 

BOILER AND ITS APPENDAGES. 

Level Gauges. — Feeding apparatus — Steam Gauge. — Barometer Gauge. 
— Safety Valves. — Self-regulating Damper. — Edelcrantz's Valve. — 
Furnace. — Smoke-consuming Furnace. — Brunton's Self-regulating Fur- 
nace. — Oldham's Modification. 117 



CONTENTS. XV 

CHAPTER IX. 

DOUBLE-CYLINDER BNOINES. 

Hornblower's Engine. — WoolPs Engine. — Cartwright's Engine. Page 134 
CHAPTER X. 

LOCOMOTIVE ENGINES ON RAILWAYS. 

High-pressure Engines. — Leopold's Engine. — Trevithick and Vivian. — 
Effects of Improvement in Locomotion. — Historical Account of the 
Locomotive Engine. — Blenkinsop's Patent. — Chapman's Improve- 
ment. — Walking Engine. — Stephenson's First Engines. — His Improve- 
ments. — Liverpool and Manchester Railway Company Their Pre- 
liminary Proceedings. — The Great Competition of 1829. — The Rocket. 
The Sanspareil. — The Novelty. — Qualities of the Rocket. — Succes- 
sive Improvements. — Experiments. — Defects of the Present Engines. 
— Inclined Planes. — Methods of surmounting them. — Circumstances of 
the Manchester Railway Company. — Probable Improvements in Loco- 
motives. — Their capabilities with respect to speed. — Probable Effects 
of the Projected Rail-roads. — Steam Power compared with Horse 
Power.^.Rail-roads compared with Canals. 145 

CHAPTER XI. 

LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 

Railway and Turnpike Roads compared. — Mr. Gurney's inventions. — 
His Locomotive Steam Engine. — Its performances. — Prejudices and 
errors. — Committee of the House of Commons. — Convenience and safe- 
ty of Steam Carriages. — Hancock's Steam Carriage.— Mr. N. Ogle. — 
Trevithick's invention.; — Proceedings against Steam Carriages. — Turn- 
pike Bills. — Steam Carriage between Gloucester and Cheltenham. — 
Its discontinuance. — Report of the Committee of the Commons. — Pre- 
sent State and Prospects of Steam Carriages. 213 

CHAPTER XII. 

STEAM NAVIGATION. 

Propulsion by paddle wheels. — Manner of driving them. — Marine Engine. 
— Its form and arrangement. — Proportion of its cylinder. — Injury to 
boilers by deposites and incrustation. — Not effectually removed by 
blowing out. — Mr. Samuel Hall's condenser. — Its advantages. Origi- 



XVI CONTENTS. 

nally suggested by Watt.— Hall's steam saver. — Howai'd's vapour en- 
gine. — Morgan's paddle wheels. — .Limits of steam navigation. — Propor- 
tion of tonnage to power. — Average speed. — Consumption of fuel. — 
Iron Steamers. — American steam raft. — Steam navigation to India. — 
By Egypt and the Red Sea to Bombay. — By same route to Calcutta. — 
By Syria and the Euphrates to Bombay. — Steam communication with 
the United States from the west coast of Ireland to St. Johns, Halifax, 
and New York. Page 241 

CHAPTER XIII. 

GENERA! ECONOMY OF STEAM POWER. 

Mechanical efficacy of steam — proportional to the quantity of water eva- 
porated, and to the fuel consumed — Independent of the pressure. — Its 
mechanical efficacy by condensation alone. — By condensation and ex- 
pansion combined — by direct pressure and expansion — by direct pres- 
sure and condensation — by direct pressure, condensation, and expan- 
sion. — The power of engines. — The duty of engines. — Meaning of horse 
power. — To compute the power of an engine. — Of the poweii of boil- 
ers. — The structure of the grate bars. — Quantity of water and steam 
room. — Fire surface and flue surface. — Dimensions of steam pipes. — 
VeLcity of piston. — Economy of fuel — Cornish duty reports. 277" 

CHAPTER XIV. 
Plain Rules for Railway Speculators. 307 



THE STEAM ENGINE 



EXPLAINED AND ILLUSTRATED. 



CHAPTER I. 



PRELIMINARY MATTER. 

Motion the Agent in Manufactures. — Animal Power. — Power depending 
on Physical Phenomena. — Purpose of a Machine. — Prime Mover. — 
Mechanical qualities of the Atmosphere. — Its Weight. — The Barome- 
ter. — Fluid Pressure. — Pressure of Karified Air. — Elasticity of Air. — 
Bellows. — Effects of Heat. — Thermometer. — Method of making one. 
— Freezing and Boiling Points. — Degrees. — Dilatation of Bodies. — 
Liquefaction and Solidification. — Vaporisation and Condensation. — 
Latent heat of Steam. — Expansion of "Water in Evaporating. — Effects 
of Repulsion and Cohesion. — Effect of Pressure upon Boiling-Point. — 
Formation of a Vacuum by Condensation. 

(1.) Of the various productions designed by nature to 
supply the wants of man, there are few which are suited to 
his necessities in the state in which the earth spontaneously 
offers them : if we except atmospheric air, we shall scarcely 
find another instance: even water, in most cases, requires 
to be transported from its streams or reservoirs; and food 
itself, in almost every form, requires culture and preparation. 
But if, from the mere necessities of physical existence in a 
primitive state, we rise to the demands of civil and social 
life — to say nothing of luxuries and refinements, — we shall 
find that everything which contributes to our convenience, 

3 



18 THE STEAM ENGINE. 

or ministers to our pleasure, requires a previous and exten- 
sive expenditure of labour. In most cases, the objects of 
our enjovment derive all their excellences, not from any 
qualities originally inherent in the natural substances out of 
which they are formed, but from those qualities which have 
been bestowed upon them by the application of human 
labour and human skill. 

In all those changes to which the raw productions of the 
earth are submitted in order to adapt them to our wants, one 
of the principal agents is motion. Thus, for example, in 
the preparation of clothing for our bodies, the various pro- 
cesses necessary for the culture of the cotton require the ap- 
plication of moving power, first to the soil, and subsequently 
to the plant from which the raw material is obtained: the 
wool must afterwards be picked and cleansed, twisted 
into threads, and woven into cloth. In all these processes 
motion is the agent: to cleanse the wool and arrange the 
fibres of the cotton, the w r ool must be beaten, teased, carded, 
and submitted to other processes, by which all the foreign 
and coarser matter may be separated, and the fibres or 
threads arranged evenly, side by side. The threads must 
then receive a rotatory motion, by which they may be twisted 
into the required form; and finally peculiar motions must 
be given to them in order to produce among them that 
arrangement which characterises the cloth which it is our 
final purpose to produce. 

In a rude state of society, the motions required in the infant 
manufactures are communicated by the immediate applica-. 
tion of the hand. Observation and reflection, however, soon 
suggest more easy and effectual means of attaining these 
ends: the strength of animals is first resorted to for the re- 
lief of human labour. Further reflection and inquiry suggest 
still better expedients. When we look around us in the 
natural world, we perceive inanimate matter undergoing 
various effects in which motion plays a conspicuous part: 
we see the falls of cataracts, the currents of rivers, the eleva- 



PRELIMINARY MATTER. 19 

tion and depression of the waters of the ocean, the currents 
of the atmosphere; .and the question instantly arises, 
whether, without sharing our own means of subsistence 
with the animals whose force we use, we may not equally, 
or more effectually, derive the powers required from these 
various phenomena of nature? A difficulty, however, im- 
mediately presents itself: we require motion of a particular 
kind; but wind will not blow, nor water fall as we please, 
nor as suits our peculiar wants, but according to the fixed 
laws of nature. We want an upward motion; water falls 
downwards : we want a circular motion; wind blows in a 
straight line. The motions, therefore, which are in actual 
existence must be modified to suit our purposes: the means 
whereby these modifications are produced, are called ma- 
chines. A machine, therefore, is an instrument interposed 
between some natural force or motion, and the object to 
which force or motion is desired to be transmitted. The 
construction of the machine is such as to modify the 
natural motion which is impressed upon it, so that it may 
transmit to the object to be moved that peculiar species of 
motion which it is required to have. To give a very ob- 
vious example, let us suppose that a circular or rotatory 
motion is required to be produced; and that the only 
natural source of motion at our command is a perpendicular 
fall of water: a wheel is provided, placed upon the axle des- 
tined to receive the rotatory motion; this wheel is furnished 
with cavities in its rim; the water is conducted into the 
cavities near the top of the wheel on one side; and being 
caught by these, its weight bears down that side of the 
wheel, the cavities on the opposite side being empty and in 
■an inverted position. As the wheel turns, the cavities on the 
descending side discharge their contents as they arrive near 
the lowest point, and ascend empty on the other side. Thus 
a load of water is continually pressing down one side of the 
wheel, from which the other side is free, and a continued 
motion of rotation is produced. 



20 THE STEAM ENGINE. 

In every machine, therefore, there are three objects de- 
manding attention:— -first, The power which imparts motion 
to it, this is called the prime mover', secondly, The nature 
of the machine itself; and thirdly, The object to which the 
motion is to be conveyed. In the steam engine the first 
mover arises from certain phenomena which are exhibited 
when heat is applied to liquids; but in the details of the 
machine and in its application there are several physical ef- 
fects brought into play, which it is necessary perfectly to 
understand before the nature of the machine or its mode of 
operation can be rendered intelligible. We propose there- 
fore to devote the present chapter to the explanation and 
illustration of these phenomena. 

(2.) The physical effects most intimately connected with 
the operations of steam engines are some of the mechanical 
properties of atmospheric air. The atmosphere is the thin 
transparent fluid in which we live and move, and which, by 
respiration, supports animal life. This fluid is apparently so 
light and attenuated, that it might be at first doubted whether 
it be really a body at all. It may therefore excite some sur- 
prise when we assert, not only that it is a body, but also 
that it is one of considerable weight. We shall be able to 
prove that it presses on every square inch* of surface with 
a weight of about 15lb. avoirdupois. 

(3.) Take a glass tube a b (fig. 2.) more than 32 inches 
long, open at one end a, and closed at the other end b, and 
let it be filled with mercury (quicksilver.) Let a glass ves- 
sel or cistern c, containing a quantity of mercury, be also 
provided. Applying the finger at a so as to prevent the 
mercury in the tube from falling out, let the tube be inverted, 
and the end, stopped by the finger, plunged into the mer- 
cury in c. When the end of the tube is below the surface 



• As we shall have frequent occasion to mention this magnitude, it 
would be well that the reader should be familiar with it. It is a square, 
each side of which is an inch. Such as a b c d, Fig. 1. 



PRELIMINARY MATTER. 21 

of the mercury in c (fig. 3.) let the finger be removed. It 
will be found that the mercury in the tube will not, as might 
be expected, fall to the level of the mercur}^ in the cistern 
c, which it would do were the end b open so as to admit the 
air into the upper part of the tube. On the other hand, the 
level d of the mercury in the tube will be about 30 inches 
above the level c of the mercury in the cistern. 

(4.) The cause of this effect is, that the weight of the 
atmosphere rests on the surface c of the mercury in the cis- 
tern, and tends thereby to press it up, or rather to resist its 
fall in the tube; and as the fall is not assisted by the weight 
of the atmosphere on the surface d (since b is closed), it fol- 
lows, that as much mercury remains suspended in the tube 
above the' level c as the weight of the atmosphere is able to 
support. 

If we suppose the section of the tube to be equal to the 
magnitude of a square inch, the weight of the column of 
mercury in the tube above the level c will be exactly equal 
to the weight of the atmosphere on each square inch of the 
surface c. The height of the level d above c being about 
30 inches, and a column of mercury two inches in height, 
and having a base of a square inch, weighing about one 
pound avoirdupois, it follows that the weight with which 
the atmosphere presses on each square inch of a level sur- 
face is about 151b. avoirdupois. 

An apparatus thus constructed, and furnished with a scale 
to indicate the height of the level d above the level c, is the 
common barometer. The difference of these levels is 
subject to a small variation, which indicates a corresponding 
change in the atmospheric pressure. But we take 30 inches 
as a standard or average. 

(5.) It is an established property of fluids that they press 
equally in all directions; and air, like every other fluid, 
participates in this quality. Hence it follows, that since 
the downward pressure or weight of the atmosphere is about 
15lb. on the square inch, the lateral, upward, and oblique 



22 THE STEAM ENGINE. 

pressures are of the same amount. But, independently of 
the general principle, it may be satisfactory to give experi- 
mental proof of this. 

Let four glass tubes a, b, c, d, (fig. 4.) be constructed of 
sufficient length, closed at one end A, b, c, d, and open at 
the other. Let the open ends of three of them be bent, as 
represented in the tubes b, c, d. Being previously filled 
with mercury, let them all be gently inverted so as to have 
their closed ends up as here represented. It will be found 
that the mercury will be sustained in -all,* and that the dif- 
ference of the levels in all will be the same. Thus the mer- 
cury is sustained in a by the upward pressure of the atmo- 
sphere, in b by its horizontal or lateral pressure, in c by its 
downward pressure, and in d by its oblique pressure; and 
as the difference of the levels is the same in all, these pres- 
sures are exactly equal. 

(6.) In the experiment described in (3.) the space b d (fig. 
3.) at the top of the tube from which the mercury has fallen 
is perfectly void and empty, containing neither air nor any 
other fluid: it is called therefore a vacuum. If, however, a 
small quantity of air be introduced into that space, it will 
immediately begin to exert a pressure on d, which will 
cause the surface d to descend, and it will continue to de- 
scend until the column of mercury c d is so far diminished 
that the weight of the atmosphere is sufficient to sustain it, 
as well as the pressure exerted upon it by the air in the 
space b d. 

The quantity of mercury which falls from the lube in this 
case is necessarily an equivalent for the pressure of the air 
introduced, so that the pressure of this air may be exactly 
ascertained by allowing about one pound per square inch 
for every two inches of mercury which has fallen from the 
tube. The pressure of the air or any other fluid above the 

* This experiment with the tube a requires to be very carefully exe- 
cuted, and the tube should be on« of small bore. 



PRELIMINARY MATTER. 23 

mercury in the tube, may at orice be ascertained by com- 
paring the height of the mercury in the tube with the height 
of the barometer; the difference of the heights will always 
determine the pressure on the surface of the mercury in the 
tube. This principle will be found of some importance in 
considering the action of the modern steam engines. 

. The air which we have supposed to be introduced into the 
upper part of the tube, presses on the surface of the mercury 
with a force much greater than its weight. For example, if 
the space b d (fig. 3.) were filled with atmospheric air in its 
ordinary state, it would exert a pressure on the surface d 
equal to the whole pressure of the atmosphere, although its 
weight might not amount to a single grain. The property 
in virtue of which the air exerts this pressure is its elasti- 
city, and this force is diminished in precisely the proportion 
in which the space which the air occupies is increased. 

Thus it is known that atmospheric air in its ordinary state 
exerts a pressure on the surface of any vessel in whick it is 
confined, amounting to about 15lb. on every square inch. 
If the capacity of the vessel which contains it be doubled, it 
immediately expands and fills the double space, but in doing 
so it loses half its elastic force, and presses only with the force 
of 7|lb. on every square inch. If the capacity of the vessel 
had been enlarged five times, the air Would still have ex- 
panded so as to fill it, but would exert only a fifth part of its 
first pressure, or 3lb. on every square inch. 

This property of losing its elastic force as its volume or 
bulk is increased, is not peculiar to air. It is common to all 
elastic fluids, and we accordingly find it in steam; and it is 
absolutely necessary to take account of it in estimating the 
effects of that agent. 

(7.) There are numerous instances of the effects of these 
properties of atmospheric air which continually fall under our 
observation. If the nozzle and valve-hole of a pair of bel- 
lows be stopped, it will require a very considerable force to 
separate the boards. This effect is produced by the diminished 



24 THE STEAM ENGINE. 

elastic force of the air remaining between the boards upon 
the least increase of the space within the bellows, while the 
atmosphere presses, with undiminished force, on the external 
surfaces of the boards. If the boards be separated so as to 
double the space within, the elastic force of the included air 
will be about 7£lb. on every square inch, while the pressure 
on the external surfaces will be 15lb. on every square inch; 
consequently, it will require as great a force to sustain the 
boards in such a position, as it would to separate them if 
each board were forced against the other, with a pressure of 
7£lb. per square inch on their external surfaces, 
y When boys apply a piece of moistened leather to a stone, 
so as to exclude the air from between them, the stone, though 
it be of considerable weight, may be lifted by a string attach- 
ed to the leather: the cause of which is the atmospheric 
pressure, which keeps the leather and the stone in close 
contact. 

(8.) the next class of physical effects which it is necessary 
to explain, are those which are produced when heat is im- 
parted or abstracted from bodies. 

In general, when heat is imparted to a body, an enlarge- 
ment of bulk will be the immediate consequence, and at the 
same time the body will become warmer to the touch. 
These two effects of expansion and increase of warmth going 
on always together, the one has been taken as a measure of 
the other; and upon this principle the common thermometer 
is constructed. That instrument consists of a tube of glass, 
terminated in a bulb, the magnitude of which is considera- 
ble, compared with the bore of the tube. The bulb and part 
of the tube are filled with mercury, or some other liquid. 
When the bulb is exposed to any source of heat, the mer- 
cury contained in it, being warmed or increased in tempera- 
ture, is at the same time increased in bulk, or expanded or 
dilated, as it is called. The bulb not having sufficient capa- 
city to contain the increased bulk of mercury, the liquid is 



PRELIMINARY MATTER. 25 

forced up in the tube, and the quantity of expansion is de- 
termined by observing the ascent of the column in the tube. 

An instrument of this kind, exposed to heat or cold, vyill 
fluctuate accordingly, the mercury rising as the heat to which 
it is exposed is increased, and falling by exposure to cold. 
In order, however, to render it an accurate measure of tem- 
perature, it is necessary to connect with it a scale by which 
the elevation or depression of the mercury in the tube may 
be measured. Such a scale is constructed for thermometers 
in this country in the following manner: — Let us suppose 
the instrument immersed in a vessel of melting ice: the 
column of mercury in the tube will be observed to fall to a 
certain point, and there maintain its position unaltered: let 
that point be marked upon the tube. Let the instrument 
be now transferred to a vessel of boiling water at a time 
when the barometer stands at the altitude of 30 inches: the 
mercury in the tube will be observed to rise until it attain a 
certain elevation, and will there maintain its position. It 
will be found, that though the water continue to be exposed 
to the action of the fire, and continue to boil, the mercury 
in the tube will not continue to rise, but will maintain a 
fixed position: let the point to which the mercury has risen, 
in this case, be likewise marked upon the tube. 

The two points, thus determined, are called the freezing 
and the boiling points. If the distance upon the tube be- 
tween these two points be divided into ISO equal parts, each 
of these parts is called a degree; and if this division be con- 
tinued, by taking equal divisions below the freezing point, 
until 32 divisions be taken, the last division is called the 
zero, or nought of the thermometer. It is the point to 
which the mercury would fall, if the thermometer were im- 
mersed in a certain mixture of snow and salt. When ther- 
mometers were first invented, this point was taken as the 
zero point, from an erroneous supposition that the tempera- 
ture of such a mixture was the lowest possible temperature. 

The degrees upon the instrument thus divided are counted 

4 



26 THE STEAM ENGINE. 

upwards from the zero, and are expressed, like the degrees 
of a circle, by placing a small ° over the number. Thus it 
will be perceived that the freezing point is 32° of our ther- 
mometer, and the boiling point will be found by adding 180° 
to 32°; it is therefore 212°. 

The temperature of a body is that elevation to which the 
thermometer would rise when the mercury enclosed in it 
would acquire the same temperature. Thus, if we should 
immerse the thermometer, and should find that the mercury 
would rise to the division marked 100°, we should then 
affirm that the temperature of the water was 100°. 

(9.) The dilatation which attends an increase of tempera- 
ture is one of the most universal effects of heat. It varies, 
however, in different bodies: it is least in solid bodies; 
greater in liquids; and greatest of all in bodies in the aeri- 
form stale. Again, different solids are differently susceptible 
of this expansion. Metals are the most susceptible of it; but 
metals of different kinds are differently expansible. 

As an increase of temperature causes an increase of bulk, 
so a diminution of temperature causes a corresponding dimi- 
nution of bulk, and the same body always has the same 
bulk at the same temperature. 

A flaccid bladder, containing a small quantity of air, will, 
when heated, become quite distended; but it will again re- 
sume its flaccid appearance when cold. A corked bottle of 
fermented liquor, placed before the fire, will burst by the 
effort of the air contained in it to expand when heated. 

Let the tube a b (fig. 5.) open at both ends, have one end 
inserted in the neck of a vessel c d, containing a coloured 
liquid, with common air above it; and let the tube be fixed 
so as to be air-tight in the neck: upon heating the vessel, the 
warm air inclosed in the vessel c d above the liquid will 
begin to expand, and will press upon the surface of the 
liquid, so as to force it up in the tube a b. 

In bridges and other structures, formed of iron, mechani- 
cal provisions are introduced to prevent the fracture or 



PRELIMINARY MATTER. 27 

strain which would take place hy the expansion and contrac- 
tion which the metal must undergo by the changes of tem- 
perature at different seasons of the year, and even at different 
hours of the day. 

Thus all nature, animate and inanimate, organized and 
unorganized, may be considered to be incessantly breathing 
heat; at one moment drawing in that principle through all 
its dimensions, and at another moment dismissing it. 

(10.) Change of bulk, however, is not the only nor the 
most striking effect which attends the increase or diminution 
of the quantity of heat in a body. In some cases, a total 
change of form and of mechanical qualities is effected by it. 
If heat be imparted in sufficient quantity to a solid body, 
that body, after a certain time, will be converted into a 
liquid. And again, if heat be imparted in sufficient quan- 
tity to this liquid, it will cease to exist in the liquid state, 
and pass into the form of vapour. 

By the abstraction of heat, a series of changes will be pro- 
duced in the opposite order. If from the vapour produced 
in this case, a sufficient quantity of heat be taken, it will re- 
turn to the liquid state; and if again from this liquid heat be 
further abstracted, it will at length resume its original solid 
state. 

The transmission of a body from the solid to the liquid 
state, by the application of heat, is called fusion or lique- 
faction, and the body is said to be fused, liquefied, or 
melted. 

The reciprocal transmission from the liquid to the solid 
state, is called congelation, or solidification; and the 
liquid is said to be congealed or solidified. 

The transmission of a body from the liquid to the vapor- 
ous or aeriform state, is called vaporization, and the 
liquid is said to be vaporized or evaporated. 

The reciprocal transmission of vapour to the liquid state 
is called condensation, and the vapour is said to be con- 
densed. 



\ 



28 THE STEAM ENGINE. 

We shall now examine more minutely the circumstances 
which attend these remarkable and important changes in 
the state of body. 

(11.) Let us suppose that a thermometer is imbedded in 
any solid body; for example, in a mass of sulphur; and that 
it stands at the ordinary temperature of 60 degrees: let the 
sulphur be placed in a vessel, and exposed to the action of 
fire. The thermometer will now be observed gradually to 
rise, and it will continue to rise until it exhibit the tempe- 
rature of 218°. Here, however, notwithstanding the con- 
tinued action of the fire upon the sulphur, the thermometer 
will become stationary; proving, that notwithstanding the 
supply of heat received from the fire, the sulphur has ceased 
to become hotter. At the moment that the thermometer 
attains this stationary point, it will be observed that the 
sulphur has commenced the process of fusion; and this pro- 
cess will be continued, the thermometer being stationary, 
until the whole mass has been liquefied. The moment the 
liquefaction is complete, the thermometer will be observed 
again to rise, and it will continue to rise until it attain the 
elevation of 570°. Here, however, it will once more be- 
come stationary; and notwithstanding the heat supplied to 
the sulphur by the fire, the liquid will cease to become 
hotter: when this happens, the sulphur will boil ; and if it 
continue to be exposed to the fire a sufficient length of time, 
it will be found that its quantity will gradually diminish, 
until at length it will all disappear from the vessel which 
contained it. The sulphur will, in fact, be converted into 
vapour. 

From this process we infer, that all the heat supplied 
during the processes of liquefaction and vaporization is con- 
sumed in effecting these changes in the state of the body; 
and that under such circumstances, it does not increase the 
temperature of the body on which the change is produced. 

These effects are general: all solid bodies would pass into 
the liquid state by a sufficient application of heat; and all 



PRELIMINARY MATTER. 29 

liquid bodies would pass into the vaporous state by the same 
means. In all cases the thermometer would be stationary 
during these changes, and consequently the temperature of 
the body, in those periods, would be maintained unaltered. 

(12.) Solids differ from one another in the temperatures 
at which they become liquid. These temperatures are 
called their melting points. Thus the melting point of 
ice is 32°; that of lead 612°; that of gold 5237°.* The 
heat which is supplied to a body during the processes of 
fusion or vaporization, and which does not affect the ther- 
mometer, or increase the temperature of the body fused or 
vaporized, is said to become latent. It can be proved to 
exist in the body fused or vaporized, and may even be taken 
from that body. In parting with it the body does not fall 
in temperature, and consequently the loss of this heat, is not 
indicated by the thermometer any more than its reception. 
The term latent heat is merely intended to express this fact, 
of the thermometer being insensible to the presence or ab- 
sence of this portion of heat, and is not intended to express 
any theoretical notions concerning it. 

(13.) In explaining the construction and operation of the 
steam engine, although it is necessary occasionally to refer 
to the effects of heat upon bodies in general, yet the body, 
which is by far the most important to be attended to, so far 
as the effects of heat upon it are concerned, is water. This 
body is observed to exist in the three different states, the 
solid, the liquid, and the vaporous, according to the varying 
temperature to which it is exposed. All the circumstances 
which have been explained in reference to metals, and the 
substance sulphur in particular, will, mutatis mutandis, 
be applicable to water. But in order perfectly to compre- 
hend the properties of the steam engine, it is necessary to 



• Temperatures above 650° cannot be measured by the mercurial 
thermometer. They can be inferred only with probability by pyro- 
meters. 



\ 



30 THE STEAM ENGINE. 

render a more rigorous and exact account of these phenome- 
na, so far as they apply to the changes produced upon water 
by the effects of heat. 

Let us suppose a mass of ice immersed in the mixture of 
snow and salt which determines the zero point of the ther- 
mometer: this mass, if allowed to continue a sufficient 
length of time submerged in the mixture, will necessarily 
acquire its temperature, and the thermometer immersed in 
it will stand at zero. Let the ice be now withdrawn from 
the mixture, still keeping the thermometer immersed in it, 
and let it be exposed to the atmosphere at the ordinary tem- 
perature, say 60°. At first the thermometer will be observed 
gradually and continuously to rise until it attain the eleva- 
tion of 32°; it will then become stationary, and the ice will 
begin to melt: the thermometer will continue standing at 
32° until the ice shall be completely liquefied. The liquid 
ice and the thermometer being contained in the same vessel, 
it will be found, when the liquefaction is completed, that the 
thermometer will again begin to rise, and will continue to 
rise until it attain the temperature of the atmosphere, viz. 
60°. Hitherto the ice or water has received a supply of 
heat from the surrounding air; but now an equilibrium of 
temperature having been established, no further supply of 
heat can be received; and if we would investigate the fur- 
ther effects of increased heat, it will be necessary to expose 
the liquid to fire, or some other source of heat. But previous 
to this, let us observe the time which the thermometer re- 
mains stationary during the liquefaction of the ice: if noted 
by a chronometer, it would be found to be a hundred and 
forty times the time during which the water in the liquid 
state was elevated one degree; the inference from which is, 
that in order to convert the solid ice into liquid water, it 
was necessary to receive from the surrounding atmosphere 
one hundred and forty times as much heat as would elevate 
the liquid water one degree in temperature; or, in other 
words, that to liquefy a given weight of ice requires as much 



/ 



PRELIMINARY MATTER. 31 

heat as would raise the same weight of water 140° in tempe- 
rature ; or from 32° to 172°. 

The latent heat of water acquired in liquefaction is there- 
fore 140°. 

(14.) Let us now suppose that, a spirit lamp being ap- 
plied to the water already raised to 60°, the effects of a 
further supply of heat be observed: the thermometer will 
continue to rise until it attain the elevation of 212°, the 
barometer being supposed to stand at 30 inches. The ther- 
mometer having attained this elevation will cease to rise; 
the water will therefore cease to become hotter, and at the 
same time bubbles of steam will be observed to be formed 
at the bottom of the vessel containing the water, near the 
flame of the spirit lamp. These bubbles will rise through 
the water, and escape at the surface, exhibiting the pheno- 
mena of ebullition, and the water will undergo the process 
of boiling. 

During this process, the thermometer will constantly be 
maintained at the same elevation of 212°; but if the time be 
noted, it will be found that the water will be altogether 
evaporated, if the same source of heat be continued to be 
applied to it six and a half times as long as was necessary to 
raise it from the freezing to the boiling point. Thus, if the 
application of the lamp to water at 32°, be capable of raising 
that water to 212° in one hour, the same lamp will require 
to be applied to the boiling water for six hours and a half, 
in order to convert the whole of it into steam. Now if the 
steam into which it is thus converted were carefully pre- 
served in a receiver, maintained at the temperature of 212°, 
this steam would be found to have that temperature, and not 
a greater one; but it would be found to fill a space about 
1700 times greater than the space it occupied in the liquid 
state, and it would possess an elastic force equal to the 
pressure of the atmosphere under which it was boiled ; that 
is to say, it would press the sides of the vessel which con- 
tained it with a pressure equivalent to that of a column of 



32 THE STEAM ENGINE. 

mercury of 30 inches in height; or what is the same thing, 
at the rate of about 15lb. on every square inch of surface. 

(15.) As the quantity of heat expended in raising the 
water from 32° to 212°, is 180°; and as the quantity of heat 
necessary to convert the same water into steam is six and a 
half times this quantity, it follows that the quantity of heat 
requisite for converting a given weight of water into steam, 
will be found, by multiplying ISO by 5§. The product of 
these numbers being 990°, it follows, that, to convert a given 
weight of water at 212° into steam of the same temperature, 
under the pressure of the atmosphere, when the barometer 
stands at 30 inches, requires as much heat as would be 
necessary to raise the same water 990° higher in tempera- 
ture. The heat, not being sensible to the thermometer, is 
latent heat ; and accordingly it may be stated, that the latent 
heat, necessary to convert water into steam under this pres- 
sure is, in round numbers, 1000°. 

(16.) All the effects of heat which we have just described 
may be satisfactorily accounted for, by supposing that the 
principle of heat imparts to the constituent atoms of bodies 
a force, by virtue of which they acquire a tendency to repel 
eacli other. But in conjunction with this, it is necessary to 
notice another force, which is known to exist in nature: 
there is observable among the corpuscles of bodies a force, 
in virtue of which they have a tendency to cohere, and col- 
lect themselves together in solid concrete masses: this force 
is called the attraction' of cohesion. These two forces — the 
natural cohesion of the particles, and the repulsive energy 
introduced by heat — are directly opposed to one another, 
and the state of the body will be decided by the predomi- 
nance of the one or the other, or their mutual equilibrium. 
If the natural cohesion of the constituent particles of the 
body considerably predominate over the repulsive energy 
introduced by the heat, then the cohesion will take effect ; 
the particles of the body will coalesce, the mass will be- 
come rigid and solid, and the particles will hold together in 



PRELIMINARY MATTER. 33 

one invariable mass, so that they cannot drop asunder by 
the mere effect of their weight. In such cases, a more or 
less considerable force must be applied, in order to break 
the body, or to tear its parts asunder. Such is the quality 
which characterises the state, which in mechanics is called 
the state of solidity. 

If the repulsive energy introduced by the application of 
heat be equal, or nearly equal, to the natural cohesion with 
which the particles of the body are endued, then the pre- 
dominance of the cohesive force may be insufficient to resist 
the tendency which the particles may have to drop asunder 
by their weight. In such a case, the constituent particles 
of the body cannot cohere in a solid mass, but will separate 
by their weight, fall asunder, and drop into the various 
corners, and adapt themselves to the shape of any vessel in 
which the body may be contained. In fact, the body will 
take the liquid form. In this slate, however, it does not 
follow that the cohesive principle will be altogether inopera- 
tive: it may, and does, in some cases, exist in a perceptible 
degree, though insufficient to resist the separate gravitation 
of the particles. The tendency which particles of liquids 
have, in some cases, to collect in globules, plainly indicates 
the predominance of the cohesive principle: drops of water 
collected upon the window pane; drops of rain condensed in 
the atmosphere; the tear which trickles on the cheek,' drops 
of mercury, which glide over any flat surface, and which it 
is difficult to subdivide or scatter into smaller parts; are all 
obvious indications of the predominance of me cohesive 
principle in liquids. 

By the due application of heat, even this small degree 
of cohesion may be conquered, and a preponderance of the 
opposite principle of repulsion may be created. But an-, 
other physical influence here interposes its aid, and conspires 
with cohesion in resisting the transmission of the body from 
the liquid to the vaporous state: this force is no other than 
the pressure of the atmosphere, already explained, This 

5 



THE STEAM ENGINE. 



pressure has an obvious tendency to restrain the particles of 
the liquid, to press them together, and to resist their separa- 
tion. The repulsive principle of the heat introduced must 
therefore not only neutralize the cohesion, but must also 
impart to the atoms of the liquid a sufficient elasticity or 
repulsive energy to enable them to fly asunder, and assume 
the vaporous form in spite of this atmospheric resistance. 

Now it is clear, that if this atmospheric resistance be sub- 
ject to any variation in its intensity, from causes whether 
natural or artificial, the repulsive energy necessary to be in- 
troduced by the heat, will vary proportionally: if the atmos- 
pheric pressure be diminished, then less heat will be neces- 
sary to vaporize the liquid. If, on the other hand, this 
pressure be increased, a greater quantity of heat will be 
required to impart the necessary elasticity. 

(17.) From this reasoning we must expect that an}' cause, 
whether natural or artificial, which diminishes the atmo- 
spheric pressure upon the surface of a liquid, will cause that 
liquid to boil at a lower temperature: and on the other hand, 
any cause which may increase the atmospheric pressure upon 
the liquid, will render it necessary to raise it to a higher 
temperature before it can boil. 

These inferences we accordingly find supported by expe- 
rience. Under a pressure of 151b. on the square inch, i. e. 
when the barometer is at 30 inches, water boils at the tem- 
perature of 212° of the common thermometer. But if 
water at a lower temperature, suppose 180°, be placed under 
the receiver of an airpump, and-, by the process of exhaus- 
tion the atmospheric pressure be -removed, or very much 
diminished, the water will boil, although its temperature 
still remain at ISCv , as may be indicated by a thermometer 
placed in it. 

On the other hand, if a thermometer be inserted air-tight 
in the lid of a close digester containing water with common 
atmospheric air above it, when the vessel is heated the air 
acquires an increased elasticity; and being confined by the 



PRELIMINARY MATTER. 35 

cover, presses, with increased force, on the surface of the 
water. By observing the thermometer while the vessel is 
exposed to the action of heat, it will be seen to rise con- 
siderably above 212°, suppose to 230°, and would continue 
so to rise until the strength of the vessel could no longer 
resist the pressure within it. 

The temperature at which water boils is commonly said 
to be 212°, which is called the boiling point of the thermo- 
meter; but, strictly speaking, this is only true when the 
barometer stands at 30 inches. If it be lower, water will 
boil at a lower temperature, because the atmospheric pres- 
sure is less; and if it be higher, as at 31, water will not boil 
until it receives a higher temperature, the pressure being 
greater. 

According as the cohesive forces of the particles of liquids 
are more or less active, they boil at greater or less tempera- 
tures. In general the lighter liquids, such as alcohol and 
ether, boil at lower temperatures. These fluids, in fact, 
would boil by merely removing the atmospheric pressure, 
as may be proved by placing them under the receiver of an 
airpump, and withdrawing the air. From this we may con- 
clude that these and similar substances would never exist in 
the liquid state at all, but for the atmospheric pressure. 

(18.) The elasticity of vapour raised from a boiling liquid, 
is equal to the pressure under which it is produced. Thus, 
steam raised from water at 212°, and, therefore, under a 
pressure of 151b. on the square inch, is endued with an 
elastic force which would exert a pressure on the sides of 
any vessel which confines it, also equal to 151b. on the 
square inch. Since an increased pressure infers an increased 
temperature in boiling, it follows, that where steam of a 
higher pressure than the atmosphere is required, it is neces- 
sary that the water should be boiled at a higher temperature. 
(19.) We have already stated that there is a certain point at 
which the temperature of a liquid will cease to rise, and that 
all the heat communicated to it beyond this is consumed in 



36 THE STEAM ENGINE. 

the formation of vapour. It has been ascertained, that when 
water boils at 212°, under a pressure equal to 30 inches 
of mercury, a cubic inch of water forms a cubic foot* of 
steam, the elastic force of which is equal to the atmospheric 
pressure, and the temperature of which is 212°. Since there 
are 1728 cubic inches in a cubic foot, it follows, that when 
water at this temperature passes from the liquid to the vapor- 
ous state, it is dilated into 1728 times its bulk. 

(20.) We have seen that about 1000 degrees of heat must 
be communicated to any given quantity of water at 212°, in 
order to convert it into steam of the same temperature, and 
possessing a pressure amounting to about 15 pounds on the 
square inch, and that such steam will occupy above 1700 
times the bulk of the water from which it was raised. Now 
we might anticipate, that by abstracting the heat thus em- 
ployed in converting the liquid into vapour, a series of 
changes would be produced exactly the reverse of those 
already described; and such is found to be actually the 
case. Let us suppose a vessel, the capacity of which is 1728 
cubic inches, to be filled with steam, of the temperature of 
212°, and exerting a pressure of 15 pounds on the square 
inch; let 5| cubic inches of water, at the temperature of 
32°, be injected into this vessel, immediately the steam will 
impart the heat, which it has absorbed in the process of 
vaporisation to the water thus injected, and will itself re- 
sume the liquid form. It will shrink into its primitive 
dimensions of one cubic inch, and the heat which it will 
dismiss will be sufficient to raise the 5h cubic inches of in- 
jected water to the temperature of 212°. The contents of 

* The terms cubic inch and cubic foot are easily explained. A common 
die, used in games of chance, has the figure which is called a cube. It 
is a solid having twelve straight edges equal to one another. It has six 
Bides, each of which is square, and which are also equal to one another. 
If its edges be each one inch in length, it is called a cubic inch, if one 
foot, a cubic foot, if one yard, a cubic yard, &c. This figure is represent- 
ed in perspective, in fig. 6. 



PRELIMINARY MATTER. 37 

the vessel will thus be 62 cubic inches of water at the tem- 
perature of 212°. One of these cubic inches is in fact the 
steam which previously filled the vessel reconverted into 
water, the other 5| are the injected water which has been 
raised from the temperature of 32° to 212° by the heat 
which has been dismissed by the steam in resuming the 
liquid state. It will be observed that in this transmission 
no temperature is lost, since the cubic inch of water into 
which the steam is converted has the same temperature as 
the steam had before the cold water was injected. 

These consequences are in perfect accordance with the 
results already obtained from observing the time necessary 
to convert a given quantity of water into steam by the 
application of heat. From the present result it follows, that 
in the reduction of a given quantity of steam to water it 
parts with as much heat as is sufficient to raise 5% cubic 
inches from 32° to 212°, that is, 5| times 180° or 990°. 

(21.) There is an effect produced in this process to which 
it is material that we should attend. The steam which filled 
the space of 1728 cubic inches shrinks when reconverted into 
water into the dimensions of 1 cubic inch. It therefore 
leaves 1727 cubic inches of the vessel it contains unoccu- 
pied. By this property steam is rendered instrumental in 
the formation of a vacuum. 

By allowing steam to circulate through .a vessel, the air 
may be expelled from it, and its place filled by steam. If 
the vessel be then closed and cooled the steam will be re- 
duced to water, and, falling in drops on the bottom and 
sides of the vessel, the space which it filled will become a 
vacuum. This may be easily established by experiment. 
Let a long glass tube be provided with a hollow ball at one 
end, and having the other end open.* Let a small quantity 
of spirits be poured in at the open end, and placing the 
glass ball over the flame of a lamp, let the spirits be boiled. 

* A common glass flask with a long 1 neck will answer the purpose. 



38 THE STEAM ENGINE. 

After some time the steam will be observed to issue copiously 
from the open end of the tube which is presented upwards. 
When this takes place, let the tube be inverted, and its open 
end plunged in a basin of cold water. The heat being thus 
removed, the cool air will reconvert the steam in the tube 
into liquid, and a vacuum will be produced, into which the 
pressure of the atmosphere on the surface of the water in 
the basin will force the water through the tube, and it will 
rush up with considerable force, and fill the glass ball. 

In this experiment it is better to use spirits than water, 
because they boil at a lower heat, and expose the glass to 
less liability to break, and also the tube may more easily be 
handled. 



CHAPTER II. 

FIRST STEPS IN THE INVENTION. 

Futility of early claims. — Watt, the real Inventor. — Hero of Alexandria. 
— Blasco Garay. — Solomon de Caus. — Giovanni Branca. — Marquis of 
Worcester. — Sir Samuel Morland. — Denis Papin. — Thomas Savery. 

(.22.) In the history of the progress of the useful arts and 
manufactures, there is perhaps no example of any invention 
the credit of which has been so keenly contested as that of 
the steam engine. Claims to it have been advanced by dif- 
ferent nations, and by different individuals of the same 
nation. The partisans of the competitors for this honour 
have argued their pretensions, and pressed their claims, 
with a zeal which has occasionally outstripped the bounds of 
discretion; and the contest has not unfrequently been tinged 
with prejudices, both national and personal, and marked 



FIRST STEPS IN THE INVENTION. 39 

with a degree of asperity quite unworthy of so noble a cause, 
and altogether beneath the dignity of science. 

The efficacy of the steam engine considered as a mechani- 
cal agent depends, first, on the several physical properties 
from which it derives its operation, and, secondly, on the 
various pieces of mechanism and details of mechanical 
arrangement by which these properties are rendered prac- 
tically available. If the merit of the invention must be 
ascribed to the discoverer and contriver of these, then the 
contest will be easily decided, because it will be obvious 
that the prize is not due to any one individual, but must be 
distributed in different proportions among several. If, how- 
ever, he is best entitled to the credit of the invention, who 
has by the powers of his mechanical genius imparted to the 
machine that form and those qualities from which it has re- 
ceived its present extensive utility, and by which it has be- 
come an agent of transcendent power, which has spread its 
beneficial effects throughout every part of the civilized globe, 
then the universal consent of mankind will, as it were by 
acclamation, award the prize to one individual, whose pre- 
eminent genius places him far above all other competitors, 
and from the application of whose mental energies to this 
machine may be dated those grand effects which have ren- 
dered it a topic of interest to every individual for whom the 
progress of human civilization has any attractions. Before 
the era marked by the discoveries of James Watt, the 
steam engine, which has since become an object of such 
universal interest, was a machine of extremely limited 
power, greatly inferior in importance to most other me- 
chanical contrivances used as prime movers. But from that 
time it is scarcely necessary here to state that it became a 
subject not of British interest only, but one with which the 
progress of the human race became intimately mixed up. 

Since, however, the question of the progressive develope- 
ment of those physical principles on which the steam engine 
depends, and of their mechanical application, has of late 



40 THE STEAM ENGINE. 

years received some importance, as well from the interest 
which the public manifest towards them as from the rank of 
the writers who have investigated them, we have thought 
it expedient to state briefly, but we trust with candour and 
fairness, the successive steps which appear to have led to 
this invention. 

The engine as it exists at present is not, strictly speaking, 
the exclusive invention of any one individual: it is the result 
. of a series of discoveries and inventions which have for the 
last two centuries been accumulating. When we attempt to 
trace back its history, and to determine its first inventor, we 
experience the same difficulty as is felt in tracing the head 
of a great river: as we ascend its course, we are embarrassed 
by the variety of its tributary streams, and find it impossible 
to decide which of those channels into which it ramifies 
ought to be regarded as the principal stream ; and it termi- 
nates at length in a number of threads of water, each in itself 
so insignificant as to be unworthy of being regarded as the 
source of the majestic object which has excited the inquiry. 

From a very early period the effects of heat upon liquids, 
and more especially the production of steam or vapour, was 
regarded as a probable source of mechanical power, and 
numerous speculators directed their attention to it, and 
exerted their inventive faculties to derive from it an effec- 
tive mover. It was not, however, until the commencement 
of the eighteenth century that any invention was produced 
which was practically applied, even unsuccessfully. All the 
attempts previous to that time were either suggestions which 
were limited to paper or experiments confined to models; or, 
if they exceeded this, they never outlived a single trial on a 
larger scale. Nevertheless many of these suggestions and 
experiments being recorded and accessible to future in- 
quirers doubtless offered useful hints and some practical aid 
to those more successful investigators who subsequently 
contrived engines in such forms as to be practically available 
on a large scale for mechanical purposes. It is right and 



FIRST STEPS IN THE INVENTION. 



41 



just, therefore— mere suggestions and abortive experiments 
though they may have been — to record them, that each in- 
ventor and discoverer may receive the just credit due to his 
share in this splendid mechanical invention. We shall then 
in the present chapter briefly enumerate, in chronological 
order, the successive steps so far as they have come to our 
knowledge. 



HERO OF ALEXANDRIA, 120 B. C. 

(23.) In a work entitled Spiritalia seu Pneumatica, 
one of the numerous works of this philosopher which has 
remained to us, is contained a description of a machine 
moved by vapour of water. A hollow sphere, of which a b 
represents a section, is supported on two pivots at a and b, 
which are the extremities of tubes a c d and b e f, which 
pass into a boiler where steam is generated. This steam 
flows through small apertures at the extremities a and b, 
and fills the hollow sphere. One or more horizontal arms 
k g, i h, project from this sphere, and are likewise filled 
with steam, but are closed at their extremities. Conceive a 

Fig. 1. 




F E 

small hole made near the extremity g, but at one side of one 
of the tubes; the steam confined in the tube and globe would 
immediately rush from the hole with a force proportionate 
to its pressure within the globe. On the common principle 

6 



42 THE STEAM ENGINE. 

of mechanics a re-action would be produced, and the tube 
would recoil in the same manner as a gun when discharged. 
The tubular arm k g being thus pressed in a direction op- 
posed to that in which the steam issues, the sphere would 
revolve accordingly, and would continue to revolve so long 
as the steam would continue to flow from the aperture. 
The force of recoil would be increased by making a similar 
aperture in two or more arms, care being taken that all the 
apertures should be placed so as to cause the sphere to re- 
volve in the same direction. 

This motion being once produced might be transmitted 
by ordinary mechanical contrivance to any machinery which 
its power might be adequate to move. 

This method of using steam is not adopted in any part or 
any form of the modern steam engine. 

BLASCO DE GAEAY, A. D. 1543. 

(24.) In the year 1826 there appeared in Zach's Corres- 
pondence a communication from Thomas Gonsalez, Director 
of the Royal Archives of Simancas, giving an account of an 
experiment reported to have been made in the year 1543 by 
order of Charles V. in the port of Barcelona. Blasco de 
Garay, a sea captain, had contrived a machine by which he 
proposed to propel vessels without oars or sails. Garay 
concealed altogether the nature of the machine which he 
used: all that was seen during the experiment was that it 
consisted of a great boiler for water, and that wheels were 
kept in revolution at each side of the vessel. The experi- 
ment was made upon a vessel called the Trinity, of 200 tons 
burden, and was witnessed by several official personages, 
whose presence on the occasion was commanded by the 
king. One of the witnesses reported that it was capable of 
moving the vessel at the rate of two leagues in three hours, 
that the machine was too complicated and expensive, and . 
was exposed to the danger of explosion. The other wit- 
nesses, however, reported more favourably. The result of 



FIRST STEPS IN THE INVENTION. 



43 



the experiment was thought to he favourable: the inventor 
was promoted, and received a pecuniary reward, besides 
having all his expenses defrayed. 

From the circumstance of the nature of the impelling 
power having been concealed by the inventor it is impossi- 
ble to say in what this machine consisted, or even whether 
steam exerted any agency whatever in it, or, if it did, 
whether it might not have been, as was most probably the 
-case, a reproduction of Hero's contrivance. It is rather 
unfavourable to the claims advanced by the advocates of the 
Spaniard, that although it is admitted that he was rewarded 
and promoted in consequence of the experiment, yet it does 
not appear that it was again tried, much less brought into 
practical use. 

SOLOMON DE CAUS, 1615. 



Fig. 2. 



(25.) A work entitled "Les Raisons des Forces Mou- 
vantes, avec diverses Machines tant utiles que plaisantes," 
published at' Frankfort in 1615, by Solomon de Caus, a 
native of France, contains the following theorem: — 

" Water will mount by the help of fire higher than its 
level," which is explained and proved in the following 
terms: — 

"The third method of raising water is by the 'aid of fire. 
On this principle may be constructed 
various machines: I shall here describe 
one. Let a ball of copper marked 
a, well soldered in every part, to 
which is attached a tube and stop, 
cock marked d, by which water may 
be introduced; and also another tube 
marked b c, which will be soldered 
into the top of the ball, and the lower 
end c of which shall descend nearly 
to the bottom of the ball without 
touching it. Let the said ball be 




44 THE STEAM'ENGINE. 

filled with water through the tube d, then shutting the stop- 
cock d, and opening the stop-cock in the vertical tube b c, 
let the ball be placed upon a fire, the heat acting upon the 
said ball will cause the water to rise in the tube b c." 

Such is the description of the apparatus of De Causas given 
by himself; and on this has been founded a claim to the in- 
vention of the steam engine. It will be observed, that neither 
in the original theorem uor in the description of the machine 
which accompanies it, is the word steam anywhere used. 
Now it was well known, by all conversant in physics, long 
before the date of the publication containing this description, 
that atmospheric air when heated acquires an increased 
elastic force. As the experiment is described, the other 
part of the ball a is filled with atmospheric air; the heat of 
the fire acting upon the air through the external surface of 
the ball, and likewise transmitted through the water, would 
of course raise the temperature of the air contained in the 
vessel, would thereby increase its elasticity, and would cause 
the water to rise in the tube b c, upon a physical principle 
altogether independent of the qualities of steam, The effect 
produced, therefore, is just what might have been expected 
by any one acquainted with the common properties of air, 
though entirely ignorant of those of steam; and, in point of 
fact, the pressure of the air is as much concerned in this 
case in raising the water as the pressure of the steam. 

This objection, however, is combated by another theorem 
contained in the same work, in which De Caus speaks of 
" the strength of the vapour produced by the action of the 
fire, which causes water to mount; which vapour will issue 
from the stop-cock with great 'violence after the water has 
been expelled." 

If De Caus be admitted to have understood the elastic 
property of the vapour of water, and to have attributed the 
ascent of the water in the tube c b to the pressure of that 
vapour upon the surface of the water confined in the copper 
ball, it must be admitted that he suggested one of the ways 



FIRST STEPS IN THE INVENTION. 45 

of using the power of steam as a mechanical agent. In the 
modern steam engine this pressure is not now used against a 
liquid surface, but against the solid surface of a piston. This, 
however, should not take from De Caus whatever credit be 
due to the suggestion of the physical property in question. 

GIOVANNI BRANCA, 1629. 

(26.) In a work published at Rome in 1629, entitled "Le 
Machine del G. Branca," is contained a description of a 
machine for propelling a wheel by a blast of steam. This 
contrivance consists of a wheel furnished with flat vanes 
upon its rim, like the boards of a paddle wheel. The steam 
is produced in a close vessel, and made to issue with violence 
from the extremity of a pipe. Being directed against the 
vanes, it causes the wheel to revolve, and this motion may 
be imparted by the usual mechanical contrivances to any 
machinery which it was intended to move. 

This contrivance has no analogy whatever to any part of 
the modern steam engines in any of their various forms. 

EDWARD SOMERSET, MARQUIS OP WORCESTER, 1 663. 

(27.) Of all the individuals to whom the invention of the 
steam engine has been ascribed the most celebrated was the 
Marquis of Worcester, the author of a work entitled " The 
Scantling of One Hundred Inventions," but which is more 
commonly known by the title " A Century of Inventions." 
It is to him that by far the greater number of writers and 
inquirers on this subject ascribe the merit of the discovery 
of the invention. This contrivance is described in the fol- 
lowing terms in the sixty-eighth invention in the work 
above named: — 

" I have invented an admirable and forcible way to drive 
up water by fire; not by drawing or sucking it upwards, for 
that must be, as the philosopher terms it, infra spseram 



46 THE STEAM ENGINE. 

activitatis, which is but at such a distance. But tins way 
hath no bounder if the vessels be strong enough. For I 
have taken a piece of whole cannon whereof the end was 
burst, and filled it three quarters full of water, stopping and 
screwing up the broken end, as also the touch-hole and 
making a constant fire under it; within twenty-four hours, 
it burst and made a great crack. So that, having a way to 
make my vessels so that they are strengthened by the force 
within them, and the one to fill after the other, I have seen 
the water run like a constant fountain stream forty feet high. 
One vessel of water rarefied by fire driveth up forty of cold, 
water, and a man that tends the work has but to turn two 
cocks ; that one vessel of water being consumed, another 
begins to foree and refill with cold water, and so sucessive- 
]y ; the fire being tended and kept constant, which the self- 
same person may likewise abundantly perform in the inte- 
rim between the necessity of turning the said cocks." 

These experiments must have been made before the year 
1663,in which the u Century of Inventions" was published. 
The description of the machine here given, like other de- 
scriptions in the same work, was only intended to express 
the effects produced, and the physical principle on which 
their production depends. It is, however, sufficiently ex- 
plicit to enable ahy one conversant with the subsequent con- 
trivance of Savery, to perceive that Lord Worcester must 
have contrived a machine containing all that part of Savery's 
engine in which the direct force of steam is employed. As 
in the above description, the separate boiler or generator of 
steam is distinctly mentioned ; that the steam from this is 
is conducted into another vessel containing the cold water to 
be raised ; that this water is raised by the pressure of steam 
acting upon its surface ; that when one vessel of water has 
thus been discharged, the steam acts upon the water con- 
tained in another vessel, while the first is being replenish- 
ed ; and that a continued upward current of water is main- 
tained by causing the steam to act alternately upon two 



FIRST STEPS IN THE INVENTION. 47 

vessels, employing the interval to fill one while the water is 
discharged from the other. 

On comparing this with the contrivance previously sug- 
gested by De Caus, .it will be observed, that even if De 
Caus knew the phyiscal agent by which the water was 
driven upwards in the apparatus contrived by him, still it 
was only a means of causing a vessel of boiling water to 
empty itself; and before a repetition of the process could be 
obtained, the vessel should be refilled, and again boiled. 
In the contrivance of Lord Worcester, on the other hand, 
the agency of the steam was employed in the same manner 
as it is in the steam engines of the present day, being gene- 
rated in one vessel, and used for mechanical purposes in an- 
other. Nor must this distinction be regarded as trifling 
and insignificant, because on it depends the whole practica- 
bility of using steam as a mechanical agent. Had its action 
been confined to the vessel in which it was produced, it 
never could have been employed for any useful purpose. 

SIR SAMUEL MORLAND, 1683. 

(28.) It appears, by a MS. in the Harleian Collection in 
the British Museum, that a mode of applying steam to raise 
water was proposed to Louis XIV. by Sir Samuel Morland. 
It contains, however, nothing more than might have been 
collected from Lord Worcester's description, and is only 
curious, because of the knowledge the writer appears to 
have had of the expansion which water undergoes in pass- 
ing into steam. The following is extracted from the MS. : 

" The principles of the new force of fire invented by 
Chevalier Morland in 1682, and presented to his Most 
Christian Majesty in 1683: — 'Water being converted into 
vapour by the force of fire, these vapours shortly require a 
greater space (about 2000 times) than the water before oc- 
cupied, and sooner than be constantly confined would split 
a piece of cannon. But being duly regulated according to 



48 THE STEAM ENGINE. 

the rules of statics, and by science reduced to measure, 
weight, and balance, then they bear their load peaceably 
(like good horses,) and thus become of great use to man- 
kind, particularly for raising water, according to the follow- 
ing table, which shows' the number of pounds that may be 
raised 1800 times per hour to a height of six inches by cy- 
linders half filled with water, as well as the different diame- 
ters and depths of the said cylinders.' " 

DENIS papin, 1695. 

(29.) Denis Papin, a native of Blois in France, and profes- 
sor of mathematics at Marbourg, had been engaged about 
this period in the contrivance of a machine in which the. 
atmospheric pressure should be made available as a mechani- 
cal agent by creating a partial vacuum in a cylinder under a 
piston. His first attempts were directed to the production 
of this vacuum by mechanical means, having proposed to 
apply a water-wheel to work an air-pump, and so maintain 
the degree of rarefaction required. This, however, would 
eventually have amounted to nothing more than a mode of 
transmitting the power of the water-wheel to another engine, 
since the vacuum produced in this way could only give back 
the power exerted by the water-wheel diminished by the 
friction of the pumps ; still this would attain the end first 
proposed by Papin, which was merely to transmit the force 
of the stream of a river, or a fall of water, to a distant point, 
by partially exhausted pipes or tubes. He next, however, 
attempted to produce a partial vacuum by the explosion of 
gunpowder ; but this was found to be insufficient, since so 
much air remained in the cylinder under the piston, that at 
least half the power due to a vacuum would have been lost. 
" I have, therefore," proceeds Papin, "attempted to attain 
this end by another method. Since water being converted 
into steam by heat acquires the property of elasticity like 
air, and may afterwards be recondenscd so perfectly by cold 



FIRST STEPS IN THE INVENTION. 49 

that there will no longer remain the appearance of elasticity 
in it, I have thought that it would not be difficult to con- 
struct machines in which, by means of a moderate heat, and 
at a small expense, water would produce that perfect vacu- 
um Which has been vainly sought by means of gunpowder." 
Papin accordingly constructed the model of a machine, 
consisting of a small pump, in which was placed a solid 
piston, and in the bottom of the cylinder under the piston 
was contained a small quantity of water. The piston being 
in immediate contact with this water, so as to exclude the 
atmospheric air, on applying fire to the bottom of the cylin- 
der steam was produced, the elastic force of which raised 
the piston to the top of the cylinder : the fire being then 
removed, and the cylinder being cooled by the surrounding 
air, the steam was condensed and reconverted into water, 
leaving a vacuum in the cylinder into which the piston was 
pressed by the force of the atmosphere. The fire being ap- 
plied and subsequently removed, another ascent and descent 
were accomplished ; and in the same manner the alternate 
motion of the piston might be continued. Papin described 
no other form of machine by which this property could be 
rendered available in practice ; but he states generally that 
the same end may be attained by various forms of machines 
easy to be imagined.* 

THOMAS SAVERY, 1698. 

(30.) The discovery of the method of producing a vacuum 
by the condensation of steam was reproduced before 1688, 
by Captain Thomas Savery, to whom a patent was granted 
in that year for a steam engine to be applied to the raising 
of water, &c. Savery proposed to combine the machine 
described by the Marquis of Worcester, with an apparatus 

* Recueil de "diverses pieces touchant quelques nouvelles machines, 
p. 38. 



50 THE STEAM ENGINE. 

for raising water by suction into a vacuum produced by the 
condensation of steam. 

Savery appears to have been ignorant of the publication 
of Papin, in 1695, and states that his discovery of the con- 
densing principle arises from the following circumstance: — 

Having drunk a flask of Florence at a tavern and flung 
the empty flask on the fire, he called for a basin of water to 
wash his hands. A small quantity which remained in the 
flask began to boil and steam issued from its mouth. It oc- 
cured to him to try what effect would be produced by in- 
verting the flask and plunging its mouth in the cold water. 
Putting on a thick glove to defend his hand from the heat, 
he seized the flask, and the moment he plunged its mouth 
in the water, the liquid immediately rushed up into the flask 
and filled it. {21.) 

Savery stated that this circumstance immediately suggest- 
ed to him the possibility of giving effect to the atmospheric 
pressure by creating a vacuum in this manner. He thought 
that if, instead of exhausting the barrel of a pump by the 
usual laborious method of a piston and sucker, it was ex- 
hausted by first filling it with steam and then condensing the 
same steam, the atmospheric pressure would force the water 
from the well into the pump-barrel and into any vessel con- 
nected with it, provided that vessel were not more than about 
34 feet above the elevation of the water in the well. He 
perceived, also, that, having lifted the water to this height, 
he might use the elastic force of steam in the manner de- 
scribed by the Marquis of Worcester to raise the same 
water to a still greater elevation, and that the same steam 
which accomplished this mechanical effect would serve by 
its subsequent condensation to repeat the vacuum and draw 
up more water. It was on this principle that Savery con- 
structed the first engine in which steam was ever brought 
into practical operation. 



51 



CHAPTER III. 



ENGINES OF SAVERY AND NEWCOMEN. 

Savery's Engine. — Boilers and their appendages. — Working apparatus. 
— Mode of Operation. — Defects of the Engine. — Newcomen and 
Cawley. — Atmospheric Engine. — Accidental Discovery of Condensa- 
tion by Jet. — Potter's Discovery of the Method of Working the 
Valves. 

(31.) The steam engine contrived by Savery, like every 
other which has since been constructed, consists of two parts 
essentially distinct. The first is that which is employed to 
generate the steam, which is called the boiler, and the 
second, that in which the steam is applied as a moving 
power. 

The former apparatus in Savery's engine consists of two 
strong boilers, sections of which are represented at d and e 
in fig. 7.; d the greater boiler, and e the less. The tubes t 
and t' communicate with the working apparatus which we 
shall presently describe. A thin plate of metal r is applied 
closely to the top of the greater boiler d turning on a centre 
c, so that by moving a lever applied to the axis c on the 
outside of the top, the sliding plate r can be brought from 
the mouth of the one tube to the mouth of the other alter- 
nately. This sliding valve is called the regulator, since it 
is by it that the communications between the boiler and two 
steam vessels (hereafter described,) are alternately opened 
and closed, the lever which effects this being constantly 
wrought by the hand of the attendant. 

Two gauge pipes are represented at g, g', the use of 
which is to determine the depth of water in the boiler. 
One g has its lower aperture a little above the proper depth, 
and the other g' a little below it. Cocks are attached to the 



52 THE STEAM ENGINE. 

upper ends g, g', which can be opened or closed at pleasure. 
The steam collected in the top of the boiler pressing on the 
surface of the water forces it up in the tubes g, g', if their 
lower ends be immersed. Upon opening the cocks g, g', if 
water be forced from, them, there is too much water in the 
boiler, since the mouth of g is below its' level. If steam 
issue from both there is too little water in the boiler, since 
the mouth of g' is above its level. But if steam issue from 
G and water from g' the water in the boiler is at its proper 
level. This ingenious contrivance for determining the level 
of the water in the boiler is the invention of Savery, and is 
used in many instances at the present day. 

The mouth of g should be at a level of a little less than 
one-third of the whole depth, and the mouth of g' at a level 
a little lower than one-third ; for it is requisite that about 
two-thirds of the boiler should be kept filled with water. 
The tube i forms a communication between the greater 
boiler d and the lesser or feeding boiler e, descending nearly 
to the bottom of it. This communication can be opened 
and closed at pleasure by the cock k. A gauge pipe is in- 
serted similar to g, g', but extending nearly to the bottom. 
From this boiler a tube p extends which is continued fo a 
cistern c (fig. 8.) and a cock is placed at m which, when 
opened, allows the water from the cistern to flow into the 
feeding boiler e, and which is closed when that boiler is 
filled. The manner in which this cistern, is supplied will 
be described hereafter. 

Let us now suppose that the principal boiler is filled to 
the level between the gauge pipes, and that the subsidiary 
boiler is nearly full of water, the cock k and the gauge cocks 
G, g' being all closed. The fire being lighted beneath d and 
the water boiled, steam is produced and is transmitted 
through one or other of the tubes t t', to the working ap- 
paratus. When evaporation has reduced the water in d be- 
low the level of g' it will be necessary to replenish the 
boiler r». This is effected thus. A fire being lighted 



SAVERV AND NEWCOMEN. 53 

beneath the feeding boiler e, steam is produced in it above 
the surface of the water, which having no escape presses on 
the surface so as to force it up in the pipe i. The cock k 
being then opened, the boiling water is forced into the prin- 
cipal boiler d, into which it is allowed to flow until water 
issues from the gauge cock g'. When this takes place, the 
cock k is closed, and the fire removed from e until the great 
boiler again wants replenishing. When the feeding boiler 
e has been exhausted, it is replenished from the cistern c 
(fig. 8.) through the pipe f by opening the cock m. 

(32.) We shall now describe the working apparatus in 
which the steam is used as a moving power. 

Let v v' (fig. 8.) be two steam vessels communicating by 
the tubes t t' (marked by the same letters in fig. 7.) with 
the greater boiler d. 

Let s be a pipe, called the suction pipe, descending into 
the well or reservoir from which the water is to be raised, 
and communicating with each of the steam vessels through 
tubes d d' by valves a a' which open upwards. Let f be a 
pipe continued from the level of the engine of whatever 
higher level it is intended to elevate the water. The steam 
vessels v v' communicate with the force-pipe f by valves 
b b' which open upward, through the tubes e e'. Over the 
steam vessels and on the force-pipe is placed a small cistern 
c already mentioned, which is kept filled with cold water 
from the force pipe, and from the bottom of which proceeds 
a pipe terminated with a cock g. This is called the con- 
densing pipe, and can be brought alternately over each 
steam vessel. From this cistern another pipe communicates 
with the feeding boiler (fig. 7.) by the cock m.* 

The communication of the pipes t t' with the boiler can 
be opened and closed, alternately, by the regulator r, (fig. 7.) 
already described. 

* This pipe in fig. 9. is represented as proceeding from the force-pipe 
above the cistern c. 



54 THE STEAM ENGINE. 

Now suppose the steam vessels and tubes to be all filled 
with common atmospheric air, and that the regulator be 
placed so that the communication between the tube t and 
the boiler be opened, the communication between the other 
tube t' and the boiler being closed, steam will flow into v 
through t. At first, while the vessel v is cold, the steam 
will be condensed and will fall in drops of water on the 
bottom and sides of the vessel. The continued supply of 
steam from the boiler will at length impart such a degree of 
heat to the vessel v that it will cease to condense it. Mixed 
With the heated air contained in the vessel v, it will have an 
elastic force greater than the atmospheric pressure, and will 
therefore force open the valve b, through which a mixture 
of air and steam will be driven until all the air in the vessel 
v will have passed out, and it will contain nothing but the 
pure vapour of water. 

When this has taken place, suppose the regulator be moved 
so as to close the communication between the tube t and the 
boiler, and to stop the further supply of steam to the vessel 
v; and at the same time let the condensing pipe g be brought 
over the vessel v and the cock opened so as to let a stream 
of cold water flow upon it. This will cool the vessel v, and 
the steam with which it is filled will be condensed and fall 
in a few drops of water, leaving the interior of the vessel a 
vacuum. The valve b will be kept closed by the atmo- 
spheric pressure. But the elastic force of the air between 
the valve a and the surface of the water in the well or re- 
servoir, will open a, so that a part of this air will rush in 
(6.) and occupy the vessel v. The air in the suction pipe s, 
being thus allowed an increased space, will be proportionably 
diminished in its elastic force (6.), and its pressure will no 
longer balance that of the atmosphere acting on the external 
surface l* of the water in the reservoir. This pressure will, 
therefore, force water up in the tube s until its weight, to- 

* Not in the diagram. 



. - SAVERY AND NEVVCOMEN. 55 

get her with the elastic force of the air above it, balances the 
atmospheric pressure on l (7.). When this has taken place, 
the water will cease to ascend. ' 

Let us now suppose that, by shifting the regulator, the com- 
munication is opened between t and the boiler, so that steam 
flows again into v. The condensing cock g being removed, 
the vessel will be again heated as before, the air expelled, 
and its place filled by the steam. The condensing pipe 
being again allowed to play upon the vessel v, and the fur- 
ther supply of steam being stopped, a vacuum will be pro- 
duced in v, and the atmospheric pressure on l will force the 
water through the valve A into the vessel v, which it will 
nearly fill, a small quantity of air, however, remaining 
above it. 

Thus far the mechanical agency employed in elevating the 
water is the atmospheric pressure; and the power of steam 
is no further employed than in the production of a vacuum. 
But, in order to continue the elevation of the water through 
the force pipe f, above the level of the steam vessel, it will 
be necessary to use the elastic pressure of the steam. The 
vessel v is now nearly filled by the water which has been 
forced into it by the atmosphere. Let us suppose that, the 
regulator being shifted again, the communication between 
the tube t and the boiler is opened, the condensing cock re- 
moved, and that steam flows into v. At first coming in con- 
tact with the cold surface of the water'and that of the vessel, 
it is condensed; but the vessel is soon heated, and the water 
formed by the condensed steam collects in a sheet or film 
on the surface of the water in v, so as to form a surface as 
hot as boiling water.* The steam then being no longer con- 
densed, presses on the surface of the water with its elastic 
force ; and when that pressure becomes greater than the 
atmospheric pressure, the valve u is forced open and the 
water, issuing through it, passes through e into the force- 

* Hot water being lighter than cold, it floats on the surface. 



56 • THE STEAM ENGINE. 

pipe f ; and this is continued until the steam has forced all 
the water from v, and occupies its place. 

The further admission of steam through t is once more 
stopped by moving the regulator; and the condensing pipe 
being again allowed to play on v, so as to condense the steam 
which fills it, produces a vacuum. Into this vacuum, as be- 
fore, the atmospheric pressure on l will force the water, and 
fill the vessel v. The condensing pipe being then closed 
and steam admitted through t, the water in v will be forced 
by its pressure through the valve b and tube e into r, and 
so the process is continued. 

We have not yet noticed the other steam vessel v', which 
as far as we have described, would have remained filled with 
common atmospheric air, the pressure of which, on the valve 
a', would have prevented the water raised in the suction 
pipe s from passing through it. However, this is not the 
case ; for, during the entire process which has been described 
in v, similar effects have been produced in v', which we have 
only omitted to notice, to avoid the confusion which the 
two processes might produce. It will be remembered, that 
after the steam, in the first instance, having flowed from the 
boiler through t, has blown the air out of v through b, the 
communication between t and the boiler is closed. Now 
the same motion of the regulator which closes this opens the 
communication between t' and the boiler; for the sliding 
plate r (fig. 7. ) is moved from the one tube to the other, 
and at the same time, as we have already stated, the con- 
densing pipe is brought to play on v. While, therefore, a 
vacuum is being formed in v by condensation, the steam, 
flowing through t', blows out the air through b', as already 
described in the other vessel v; and, while the air in s is 
rushing up through a into v followed by the water raised 
in s by the atmospheric pressure on l, the vessel v' is 
being filled with steam, and the air is completely expelled 
from it. 

The communication between t and the boiler is now 



SAVERY AND NEWCOMEN. 57 

again opened, and the communication between t' and the 
boiler closed by moving the regulator r (fig. 7.) from the 
tube t to t' ; at the same time the condensing pipe is re- 
moved from over v- and brought to play upon v'. While 
the steam once more expels the air from v through b, a va- 
cuum is formed by condensation in v\ into which the 
water in s rushes through the valve a'. In the mean time 
v is again filled with steam. The communication between 
T and the boiler is now closed, and that between t' and the 
boiler is opened, and the condensing pipe removed from v' 
and brought to play on v. While the steam from the boil- 
er forces the water in v' through b' into the force-pipe f, a 
vacuum is being produced in v into which water is raised 
by the atmospheric pressure at l. 

Thus each of the vessels v v' is alternately filled from s 
and the water thence forced into r. The same steam which 
forces the water from the vessels into r, having done its 
duty, is condensed, and brings up the water from s by 
giving effect to the atmospheric pressure. 

During this process, two alternate* motions or adjustments 
must be constantly made ; the communication between t 
and the boiler must be opened, and that between t' and the 
boiler closed, which is done by one motion of the regulator. 
The condensing pipe at the same time must be brought 
from v to play on v' which is done by the lever placed up- 
on it. Again the communication between t' and the boiler 
is to be opened, and that between t and the boiler closed ; 
this is done by moving back the regulator. The condensing 
pipe is brought from v' to v by moving back the other lever, 
and so on alternately. 

For the clearness and convenience of description, some 
slight and otherwise unimportant changes have been made 
in the position of the parts.* A perspective view of this 

* In the diagrams used for explaining the principles and operations of 
machines, I have found it contribute much to the clearness of the descrip- 

S 



58 THE STEAM ENGINE. 

engine is presented in fig. 9. The different parts already 
described will easily be recognised, being marked with the 
same letters as in figs. 6, 7. 

(33.) In order duly to appreciate the value of improve- 
ments, it is necessary first to perceive the defects which 
these improvements are designed to remove. Savery's 
steam engine, considering how little was known of the value 
and properties of steam, and how low the general standard 
of mechanical knowledge was in his day, is certainly high- 
ly creditable to his genius. Nevertheless it had very con- 
siderable defects, and was finally found to be inefficient for 
the most important purposes to which he proposed apply- 
ing it. 

At the time of this invention^ the mines in England had 
greatly increased in depth, and the process of draining them 
had become both expensive and diificult ; so much so, that 
it was found in many instances that their produce did not 
cover the cost of working them. The drainage of these 
mines was the most important purpose to which Savery 
proposed to apply his stfeam engine. 

It has been already stated, that the pressure of the atmo- 
sphere amounts to about 15 lbs. (3.) on every square inch. 
Now, a column of water, whose base is one square inch, and 
whose height is 34 feet, weighs about 15ibs. If. we suppose 
that a perfect vacuum were produced in the steam-vessels v 
v' (fig. 8.) by condensation, the atmospheric pressure on l 
would fail to force up the water, if the height of the top of 
these vessels exceeded 34 feet. It is plain, therefore, that 
the engine cannot be more than 34 feet above the water 
which it is intended to elevate. But in fact it cannot be so 
much ; for the vacuum produced in the steam-vessels v v' 

lion to adopt an arrangement of parts somewhat different from that of 
the real machine. When once the nature and principles on which the 
machine acts are well understood, the reader will find no difficulty in 
transferring every part to its proper place, which is represented in the 
perspective drawings. 



SAVE BY AND NEWCOMEN. 5U 

is never perfect. Water, when not submitted to the pres- 
sure of the atmosphere, will vaporise at a very low tempe- 
rature (17. ); and it was found that a vapour possessing a 
considerable elasticity would, notwithstanding the conden- 
sation, remain in the vessels v v' and the pipe s, and would 
oppose the ascent of the water. In consequence of this, it 
was found that the engine could never be placed with prac- 
tical advantage at a greater height than 26 feet above the 
level of the water to be raised. 

(34.) When the water is elevated to the engine, and the 
steam-vessels filled, if steam be introduced above the water 
in v, it must first balance the atmospheric pressure, before it 
can force the water through the valve b. Here, then, is a 
mechanical pressure of I5lbs. per square inch expended, 
without any water being raised by it. If steam of twice 
that elastic force be used, it will elevate a column in f of 
34 feet in height ; and if steam of triple the force be used, 
it will raise a column of 68 feet high, which, added to 26 
feet raised by the atmosphere, gives a total lift of 94 feet. 

In effecting this, steam of a pressure equal to three times 
that of the atmosphere acts on the inner surface of the ves- 
sels v v'. One third of this bursting of the pressure is ba- 
lanced by the pressure of the atmosphere on the external 
surface of the vessels ; but an effective pressure of 30lbs. per 
square inch still remains, tending to burst the vessels. It 
was found, that the apparatus could not be. constructed to 
bear more than this with safety; and, therefore, in practice 
the lift of such an engine was limited to about 90 perpen- 
dicular feet. In order to raise the water from the bottom 
of the mine by these engines, therefore, it was necessary to 
place one at every 90 feet of the depth ; so that the water 
raised by one through the first 90 feet should be received 
in a reservoir, from which it was to be elevated the next 
90 feet by another, and so on. 

Besides this, it was found that sufficient strength could 
not be given to those engines, if constructed upon a large 



60 THE STEAM ENGINE. 

scale. They were, therefore, necessarily very limited in 
their dimensions, and were incapable of raising the water 
with sufficient speed. Hence arose a necessity for several 
engines at each level, which greatly enhanced the expense. 

(35.) These, however, were not the only defects of Sa- 
very's engines. The consumption of fuel was enormous, 
the proportion of heat wasted being much more than what 
was used in either forcing up the water, or producing a va- 
cuum. This will be very easily understood by attending 
to the process of working the engine already described. 

When the steam is first introduced from the boiler into 
the steam-vessels v v', preparatory to the formation of a 
vacuum, it is necessary that it should heat these vessels up to 
the temperature of the steam itself; for until then the steam 
will be condensed the moment it enters the vessel by the 
cool surface. All this heat, therefore, spent in raising the 
temperature of the steam vessels is wasted. Again, when 
the water has ascended and filled the vessels v v', and steam 
is introduced to force this water through b b' into f, it is 
immediately condensed by the cold surface in v v', and 
does not begin to act until a quantity of hot water, formed 
by condensed steam, is collected on the surface of the cold 
water which fills the vessel v v'. Hence another source of 
the waste of heat arises. 

When the steam begins to act upon the surface of the 
water in v v', and to force it down, the cold surface of the 
vessel is gradually exposed to the steam, and must be heat- 
ed while the steam continues its action ; and when the water 
has been forced out of the vessel, the vessel itself has been 
heated to the temperature of the steam which fills it, all 
which heat is dissipated by the subsequent process of con- 
densation. It must thus be evident that the steam used in 
forcing up the water in r, and in producing a vacuum, bears 
a very small proportion indeed to what is consumed in heat- 
ing the apparatus after condensation. 



PI. I. 



Fig. 4. 




J'.n^i-.l.rr.Mxwerifk. 



"?:. 



SAVERT AND NEWCOMEN. 61 

(36.) There is also another circumstance which increases 
the consumption of fuel; The water must be forced through 
b, not. only against the atmospheric pressure, but also against 
a column of 6S feet of water. Steam is therefore required of 
a pressure of 45lbs. on the square inch. Consequently the 
water in the boiler must be boiled under this pressure. That 
this should take place, it is necessary that the water should 
be raised to a temperature considerably above 212° (17.), 
even so high as 267°; and thus an increased heat must be 
given to the boiler. Independently of the other defects, 
this intense heat weakened and gradually destroyed the ap- 
paratus. 

Besides the drainage of mines, Savery proposed to apply 
his steam engine to a variety of other purposes ; such as 
supplying cities with water, ' forming ornamental water- 
works in pleasure grounds, turning mills, &c. 

Savery was the first who suggested the method of express- 
ing the power of an engine with reference to that of horses. 
In this comparison, however, he supposed each horse to 
work but 8 hours a day, while the engine works for 24 
hours. This method of expressing the power . of steam 
engines will be explained hereafter. 

(37.) The failure of the engines proposed by Captain 
Savery in the great work of drainage, from the causes which 
have been just mentioned and the increasing necessity for 
effecting this object arising from the circumstance of the 
large property in mines, which became every year unpro- 
ductive by it, stimulated the ingenuity of mechanics to con- 
trive some means. of rendering those powers of steam exhi- 
bited in Savery's engine practically available. Among 
others, Thomas Newcomen, a blacksmith of Dartmouth, and 
John Cawley, a plumber of the same place, turned their at- 
tention to this inquiry. 

Newcomen appears to have resumed the old method of 
raising the water from the mines by ordinary pumps, but 
conceived the idea of working these pumps by some moving 



62 THE STEAM ENGINE. 

power less expensive than that of horses. The means 
whereby he proposed effecting this was by connecting the 
end of a pump rod d (fig. 10.), by a chain, with the arch head 
A of a working beam a b, playing on anaxis c. The other 
arch head b of this beam was connected by a chain with the 
rod e of a solid piston p, which moved air-tight in a cylinder 
f. If a vacuum be created beneath the pislon p, the atmo- 
spheric pressure acting upon it will press it down with a 
force of 15 lbs. per square inch ; and the end a of the beam 
being thus raised, the pump-rod d will be drawn up. If a 
pressure equivalent to the atmosphere be then introduced 
below the piston, so as to neulralize the downward pressure, 
the piston will be in a stale of indifference as to rising or 
falling ; and if in this case the rod p be made heavier than 
the piston and its rod, so as to overcome the friction, &c. it 
will descend, and elevate the piston again to the top of the 
cylinder. The vacuum being again produced, another descent 
of the piston, and consequent elevation of the pump-rod, will 
take place ; and so the process may be continued. 

Such was Newcomen's first conception of the atmospheric 
engine; and the contrivance had much, even at the' first 
view, to recommend it. The power of such a machine 
would depend entirely on the magnitude of the piston ; and 
being independent of a highly elastic steam, would not 
expose the materials to the destructive heat which was 
necessary for working Savery's engine. Supposing a per- 
fect vacuum to be produced under the piston in the cylinder, 
an effective downward pressure would be obtained, amount- 
ing to 15 times as many pounds as there are square inches 
in the section of the piston.* Thus, if the base of the piston 

* As the calculation of the power of an engine depends on the number 
of square inches in the section of the piston, it may be useful to give a 
rule for computing the number of square inches in a circle. The follow- 
ing rule will always give the dimensions with sufficient accuracy: — 
Multiply the number of inches in the. diameter by itself; divide the product 
by 14, and multiply the quotient thus obtained by 11, arid the result will be 



EL II. 



&</' ^ 



£^j SAYETBtTS STEAM EW'CTiW, 




Engr. by P.Mhverick.. 



SAVERY AND NEWCOMEN. 63 

were 100 square inches, a pressure equal to I500lbs. would 
be obtained. 

(38.) In order to accomplish this design, two things were 
necessary: 1. To make a speedy and effectual vacuum below 
the piston in the descent; and 2. To contrive a counterpoise 
for the atmosphere in the ascent. 

The condensation of steam immediately presented itself 
as the most effectual means of accomplishing the former; 
and the elastic force of the same steam previous to conden- 
sation an obvious method of effecting the latter. Nothing 
now remained to carry the design into execution, but the 
contrivance of means for the alternate introduction and con- 
densation of the steam; and Newcornen and Cawley were 
accordingly granted a patent in 1707, in which Savery wa3 
united, in consequence of the principle of condensation for 
which he had previously received a patent being necessary 
to the projected machine. We shall now describe the atmo- 
spheric engine, as first constructed by Newcornen: — 

The boiler k is placed over a furnace i, the flue of which 
winds round it, so as to communicate heat to every pari of 
the bottom of it. In the top, which is hemispherical, two 
guage pipes g g' are placed, as in Savery's engine, and a 
puppet valve v, which opens upward, and is loaded at one 
pound per square inch ; so that when the steam produced in 
the boiler exceeds the pressure of the atmosphere by more 
than one pound on the square inch, the valve v is lifted, and 
the steam escapes through it, and continues to escape until 
its pressure is sufficiently diminished, when the valve v 
again falls into its seat. 

The great steam-tube is represented at s, which conducts 



the number of square inches in the circle. Thus if there be 12 inches in 
the diameter, this multiplied by istelf gives 144, which divided by 14 
gives 10 T \, which multiplied by 11 gives 115, neglecting fractions. 
There are, therefore, 115 square inches in a circle whose diameter is 12 
inches. 



64 THE STEAM ENGINE. 

steam from the boiler to the cylinder; and a feeding pipe t 
furnished with a cock, which is opened and closed at plea- 
sure, proceeds from a cistern e to the' boiler. By this pipe 
the boiler may be replenished from the cistern, when the 
gauge cock g' indicates that the level has fallen below it. 
The cistern e is supplied with hot water by means which we 
shall presently explain. 

(39.) To understand the mechanism necessary to work 
the piston, let us consider how the supply and condensation 
of steam must be regulated. When the piston has been 
forced to the bottom of the cylinder by the atmospheric 
pressure acting against a vacuum, in order to balance that 
pressure, and enable it to be drawn up by the weight of the 
pump-rod, it is necessary to introduce steam from the boiler. 
This is accomplished by opening the cock r in the steam- 
pipe s. The steam being thus introduced from the boiler, 
its pressure balances the action of the atmosphere upon the 
piston, which is immediately drawn to the top of the cylinder 
by the weight of the pump-rod d. It then becomes neces- 
sary to condense this steam, in order to produce a vacuum. 
To accomplish this the further supply of steam must be cut 
off, which is done by closing the cock k. The supply of 
steam from the boiler being thus suspended, the diffusion of 
cold water on the external surface of the cylinder becomes 
necessary to condense the steam within it. This was done 
by enclosing the cylinder within another, leaving a space 
between them.* Into this space cold water is allowed to 
flow from a cock m placed oVer it, which is supplied by a 
pipe from the cistern n. This cistern is supplied with water 
by a pump o, which is worked by the engine itself, from 
the beam above it. 

The cold water supplied from m, having filled the space 
between the two cylinders, abstracts the heat from the inner 
one; and condensing the steam, produces a vacuum, into 

* The external cylinder is not represented in the diagram. 



SAVERY AND NEWCOMEN. 65 

which the piston is immediately forced by the atmospheric 
pressure. Preparatory to the next descent, the water which 
thus fills the space between the cylinders, and which is 
warmed by the heat it has abstracted from the steam, must 
be discharged, in order to give room for a fresh supply of 
cold water from m. An aperture, furnished with a cock, is 
accordingly provided in the bottom of the cylinder, through 
which the water is discharged into the cistern l ; and being 
warm, is adapted for the supply of the boiler through t, as 
already mentioned. 

The cock r being now again opened, steam is admitted 
below the piston, which, as before, ascends, and the descent 
is again accomplished by opening the cockM, admitting cold 
water between the cylinders, and thereby condensing the 
steam below the piston. 

The condensed steam, thus reduced to water, will collect 
in the bottom of the cylinder, and resist the descent of the 
piston. It is, therefore, necessary to provide an exit for it, 
which is done by a valve opening outwards into a tube 
which leads to the feeding cistern l, into which the con- 
densed steam is driven. 

That the piston should continue to be air-tight, it was 
necessary to keep a constant supply of water over it; this 
was done by a cock similar to m, which allowed water to 
flow from the pipe m on the piston. 

(40.) Soon after the first construction of these engines, an 
accidental circumstance suggested to Newcomen a much 
better method of condensation than the effusion of cold 
water on the external surface of the cylinder. An engine 
was observed to work several strokes with unusual rapidity, 
and without the regular supply of the condensing water. 
Upon examining the piston, a hole was found in it, through 
which the water, which was poured on to keep it air-tight, 
flowed, and instantly condensed the steam under it. 

On this suggestion Newcomen abandoned the external 
cylinder, and introduced a pipe h furnished with a cock q 

9 



66 THE STEAM ENGINE. 

into the bottom of the cylinder, so that on turning the cock 
the pressure of the water in the pipe h, from the level of the 
water in the cistern n, would force the water to rise as a jet 
into the cylinder, and would instantly condense the steam* 
This method of condensing by a jet formed a very important 
improvement in the engine, and is the method still used. 
- (41.) Having taken a general view of the parts of the at- 
mospheric engine, let us now consider more particularly its 
operation. 

When the engine is not working the weight of the pump- 
rod d draws down the beam A, and draws the piston to the 
top of the cylinder, where it rests. Let us suppose all the 
cocks and valves closed, and the boiler filled to the proper 
depth. The fire being lighted beneath it, the water is boiled 
until the steam acquires sufficient force to lift the valve v. 
When this takes place, the engine may be started. For this 
purpose the regulating valve n is opened. The steam rushes 
in and is first condensed by the cold cylinder. After a short 
trme the cylinder acquires the temperature of the steam, 
which then ceases to be condensed, and mixes with the air 
which filled the cylinder. The steam and heated air, having 
a greater force than the atmospheric pressure, will open a 
valve placed at the end x of a small tube in the bottom of 
the cylinder, and which opens outwards. From this (which 
is called the blowing valve*) the steam and air rush in a 
constant stream until all the air has been expelled, and the 
cylinder is filled with the pure vapour of water. This pro- 
cess is called blowing the engine preparatory to starting it. 
When it is about to be started, the engine-man closes the 
regulator k, and thereby suspends the supply of steam from 
the boiler. At the same time he opens the condensing 
valve H;t and thereby throws up a jet of cold water into the 
cylinder. This immediately condenses the steam contained 

* Also called the snifting valve, from the peculiar noise made by the 
air and steam escaping 1 from it. 
f Also called the injection valve. 



SAVERY AND NEWCOMEN. G7 

in the c}']inder, and produces the vacuum. (The atmosphere 
cannot enter the blowing valve, because it opens outwards, 
so that no air can enter to vitiate the vacuum.) The atmo- 
spheric pressure above the piston now takes effect, and 
forces it down in the cylinder. The descent being com- 
pleted, the engine-man closes the condensing valve h, and 
opens the regulator r. By this means he stops the play of 
the jet within the cylinder, and admits the steam from the 
boiler. The first effect of the steam is to expel the con- 
densing water and condensed steam which are collected in 
the bottom of the cylinder through the tube r, containing a 
valve which opens outwards, (called the eduction valve,) 
which leads to the hot cistern l, into which this water is 
therefore discharged. 

When the steam admitted through r ceases to be con- 
densed, it balances the atmospheric pressure above the piston, 
and thus permits it to be drawn to the top of the cylinder 
by the weight of the rod d. This ascent of the piston is 
also assisted by the circumstance of the steam being some- 
what stronger than the atmosphere. 

When the piston has reached the top, the regulating valve 
r is closed, and-the condensing valve h opened, and another 
descent produced as before, and so the process is continued. 
The manipulation necessary in working this engine was, 
therefore, the alternate opening and closing of two valves; 
the regulating and condensing valves. When the piston 
reached the top of the cylinder, the former was to be closed, 
and the latter opened; and, on reaching the bottom, the for- 
mer was to be opened, and the latter closed. 

(42.) From the imperfect attention which even an assidu- 
ous attendant could give to the management of these valves, 
the performance of the engines was very irregular, and the 
waste of fuel very great, until a boy named Humphrey 
Potter contrived means of making the engine work its own 
valves. This contrivance, although made with no other 
design than the indulgence of an idle disposition, neverthe- 



68 THE STEAM ENGINE. 

less constituted a most important step in the progressive 
improvement of the steam-engine; for by its means, not 
only the irregularity arising from the negligence of attend- 
ants was avoided, but the speed of the engine was doubled. 

Potter attached strings to the levers which worked the 
valves, and carrying these strings to the working beam, 
fastened them upon it in such a manner that as the beam 
ascended and descended, it pulled the strings so as to open 
and close the proper valves with the most perfect regularity 
and certainty. This contrivance was afterwards much im- 
proved by an engineer named Beighton, who attached to 
the working beam a straight beam called a plug frame, 
carrying pins which, in the ascent and descent of the beam, 
struck the levers attached to the valves, and opened and 
closed them exactly at the proper moment. 

The engine thus improved required no other attendance 
except to feed the boiler occasionally by the cock t, and to 
attend the furnace. 



G9 



CHAP. IV. 



ENGINE OF JAMES WATT. 



Advantages of the Atmospheric Engine over that of Captain Savery. — It 
contained no new Principle. — Papin's Engine. — James Watt. — Partic- 
ulars of his Life. — His first conceptions of the means of Economising 
- Heat. — Principle of his projected Improvements. 

(43.) Considered practically, the engine described in the 
last chapter possessed considerable advantages over that of 
Savery ; and even at the present day this machine is not 
unfrequently used in districts where fuel is very abundant 
and cheap, the first cost being considerably less than that of 
a modern engine. The low pressure of the steam necessary 
to work it rendered the use of the atmospheric engine per- 
fectly safe ; there being only a bursting pressure of about 
lib. per inch, while in Savery's there was a bursting pres- 
sure amounting to 30lbs. The temperature of the steam 
not exceeding 216°, did not weaken or destroy the materials; 
while Savery's engines required steam raised from water at 
267°, which in a short time rendered the engine unable to 
sustain the pressure. 

The power of Savery's engines was also very limited, 
both as to the quantity of water raised, and the height to 
which it was elevated (34.). On the other hand, the atmo- 
spheric engine had no other limit than the dimensions of the 
piston. In estimating the power of these engines, however, 
we cannot allow the full atmospheric pressure as an effective 
force. The condensing water being mixed with the con- 
densed steam, forms a quantity of hot water in the bottom 
of the cylinder, which, not being submitted to the atmos- 
pheric pressure (17.), produces a vapour which resists the 
descent of the piston. In practice we find that an allow- 



70 THE STEAM ENGINE. . 

ance of at least 3lbs. per square inch should be made for the 
resistance of this vapour, and lib. per square inch for fric- 
tion, &c. ; so that the effective force will be found by sub- 
tracting these 4lbs. per square inch from the atmospheric 
pressure ; which, if estimated at 15lbs., leaves an effective 
working power of about lllbs. per square inch. This, 
however, is rather above what is commonly obtained. 

Another advantage which this engine has over those of 
Savery, is the facility with which it might be applied to 
drive machinery by means of the working beam. 

The merit of this engine as an invention, must be ascribed 
principally to its mechanism and combinations. We find in it 
no new principle; the agency of atmospheric pressure acting 
against a vacuum, or a partial vacuum, was long known. 
The formation of a vacuum by the condensation of steam had 
been suggested by Papin and Savery, and carried into prac- 
tical effect by the latter. The mechanical power deriveable 
from the direct pressure of the elastic force of steam was 
distinctly pointed out by Lord Worcester, and even prior 
to his time; the boiler, gauge pipes, and regulator of the 
atmospheric engine, were evidently borrowed from Savery's 
engine. The idea of working a piston in a cylinder by 
the atmospheric pressure against a vacuum below, was sug- 
gested by Otto Guericke, an ingenious German philosopher, 
the inventor of the air pump, and subsequently by Papin ; 
and the use of a working beam could hot have been unknown. 
Nevertheless, considerable credit must be acknowledged to 
be due to Newcomen for the judicious combination of those 
scattered principles. . "The mechanism contrived by him," 
says Tredgold, " produces all the difference between an effi- 
cient and inefficient engine, and should be more highly 
valued than the fortuitous discovery of a new principle." 
The rapid condensation of steam by the injection of water, 
the method of clearing the cylinder of air and water after 
the stroke, are two contrivances not before in use, and which 
are quite essential to the effective operation of the engine : 
these are wholly due to Newcomen and his associates. 



JAMES WATT. 71 

(44.) The patent , of Newcomen was granted in 1705 ; and 
in 1707, Papin published a work, entitled "A New Method 
of raising Water by Fire," in which a steam engine is 
described, which would scarcely merit notice here but for 
the contests which have arisen upon the claims of different 
nations for a share in the invention of the steam engine. 
The publication of this work of Papin was nine years after 
Savery's patent, with which he acknowledges himself ac- 
quainted, and two years after Newcomen's. The following 
is a description of Papin's steam engine: — 

An oval boiler, a (fig. 11.), is filled to about two thirds of 
its entire capacity with water, through a valve b in the top, 
which opens upwards, and is kept down by a lever carrying 
a sliding weight. The pressure on the valve is regulated 
by moving the weight to or from b, like the common steel- 
yard. This boiler communicates with a cylinder, c, by a 
syphon tube furnished with a stopcock at d. The cylinder 
c has a valve f in the top, closed by a lever and weight 
similax v to b, and a tube with a stopcock a opening into the 
atmosphere. In this cylinder is placed a hollow copper 
piston h, which moves freely in it, and floats upon the water. 
Another tube forms a communication between the bottom of 
this cylinder and the bottom of a close cylindrical vessel i, 
called the air vessel. In this tube is a valve at it, opening 
upwards; also a pipe terminated in a funnel, and furnished 
with a valve L, which opens downwards. From the lower 
part of the air-vessel a tube proceeds, furnished also with a 
stopcock m, which is continued to whatever height the water 
is to be raised. 

Water being poured into the funnel, passes through the 
valve l, which opens downwards; and filling the tube, as- 
cends into the cylinder c, carrying the floating piston h on 
its surface, and maintains the same level in c which it has in 
the funnel. In this manner the cylinder c may be filled to 
the level of the top of the funnel. In this process the cock 
G should be left open, to allow the air in the cylinder to es- 
cape as the water rises. 



72 THE STEAM ENGINE. 

Let us now suppose that, a fire being placed beneath the 
boiler, steam is being produced. On opening the cock d, 
and closing g, the steam, flowing through the syphon tube 
into the top of the cylinder, presses down the floating piston, 
and forces the water into the lower tube. The passage at l 
being stopped, since l opens downwards, the water forces 
open the valve k, and passes into the air vessel i. When the 
piston h has been forced to the bottom of the cylinder, the 
cock d is closed, and g is opened, and the steam allowed to 
escape into the atmosphere. The cylinder is then replenished 
from the funnel as before; and the cock g being closed, and 
d opened, the process is repeated, and more water forced 
into the air-vessel i. 

By continuing this process, water is forced into the air- 
vessel, and the air which originally filled that vessel is com- 
pressed into the space above the water ; and its elastic force 
increases exactly in the same proportion as its bulk is di- 
minished. (6.) Now, suppose that half of the vessel i has 
been filled by the water which is forced in, the air above 
the water being reduced to half its bulk has acquired twice 
the elastic force, and therefore presses on the surface of the 
water with twice the pressure of the atmosphere. Again, 
if two thirds of the air vessel be filled with water, the air is 
compressed into one third of its bulk, and presses on the 
surface of the water with three times the pressure of the 
atmosphere, and so on. 

Now if the cock m be opened, the pressure of the con- 
densed air will force the water up in the tube n, and it will 
continue to rise until the column balances the pressure of 
the condensed air. If, when the water is suspended in the 
tube, and the cock m open, the vessel i is half filled, the 
height of the column in n will be 34 feet, because 34 feet of 
water has a pressure equal to the atmosphere ; and this, 
added to the atmospheric pressure on it, gives a total pres- 
sure equal to twice that of the atmosphere, which balances 
the pressure of the air in i reduced to half its bulk. If two 



PI. III. 




Drawn by tfie Author. 



JSm/r. byHMavei 



JAMES WATT. 73 

thirds of i be filled with water, a column of 68 feet will be 
supported in n ; for such a column, united with the' atmo- 
spheric pressure on it, gives a total pressure equal to three 
times that of the atmosphere, which balances the air in i 
compressed into one third of its original bulk. 

By omitting the principle of condensation, this machine 
loses 26 feet in the perpendicular lift. But, indeed, in 
every point of view, it is inferior to the engines of Savery 
and Newcomen. 

(45.) From the construction of the atmospheric engine by 
Newcomen, in 1705, for about half a century, no very im- 
portant step had been made in the improvement of the 
steam engine. During this time the celebrated Smeaton 
had given much attention to the details of the atmospheric 
engine, and brought that machine to as high a state of per- 
fection as its principle seemed to admit, and as it has ever 
since reached. 

In the year 1763, James Watt, a name illustrious in the 
history of mechanical science, commenced his experiments 
on steam. He was born at Greenock, in the year 1736; 
and at the age of 16 was apprenticed to a mathematical in- 
strument-maker, with whom he spent four years. At the 
age of 20 he removed to London, where he still pursued 
the same trade under a mathematical instrument-maker in 
that city. After a short time, however, finding his health 
declining, he returned to Scotland, and commenced business 
on his own account at Glasgow. In 1757 he was appoint- 
ed mathematical instrument-maker to the university of Glas- 
gow, where he resided and earned on business. 

This circumstance produced an acquaintance between him 
and the celebrated Dr. Robison, then a student in Glasgow, 
who directed Watt's attention to the steam engine. In his 
first experiments he used steam of a high pressure; but 
found it attended with so much danger of bursting the 
boiler, and difficulty of keeping the joints tight, and other 
objections, that he relinquished the inquiry at that time. 

10 



74 . ' THE STEAM ENGINE.. 

(46.) In the winter of 1763, Watt was employed to re- 
pair the model of an atmospheric engine, belonging to. the 
natural philosophy class in the university — a circumstance 
which again turned his attention to the subject of the steam 
engine. He found the consumption of steam in working 
this model so great, that he inferred that the quantity 
wasted, must have had a very large proportion to that used 
in working the piston. His first conclusion was, that the 
material of the cylinder (brass) was too good a conductor of 
heat, and that much was thereby lost. He made some ex- 
periments, accordingly, with wooden cylinders, soaked -in 
linseed oil, which, however,- he soon laid aside. Further 
consideration cohvinced him that a prodigious waste of steam 
was essential to the very principle of the atmospheric engine. 
This will be easily understood. 

When the steam has filled the cylinder so as to balance 
the atmospheric pressure on the piston, the cylinder must 
have the same temperature as the steam itself. Now,, on 
introducing the condensing jet, the steam mixed with this 
water forms a mass of hot water in the bottom of the cylin- 
der. This water, hot being under the atmospheric pressure, 
boils at very low temperatures, and produces a vapour which 
resists the descent of the piston. 

The heat of the cylinder itself assists this process; so that 
in order to produce a tolerably perfect vacuum, it was found 
necessary to introduce a quantity of condensing water, suffi- 
cient to reduce the temperature of the water in the cylinder 
lower than 100°, and consequently: to eool the cylinder itself, 
to that temperature. Under these circumstances, the descent 
of the piston was found to suffer very little resistance from 
any vapour within the cylinder: but then on the subsequent 
ascent, an immense waste of steam ensued ; for the steam, 
on being admitted under the piston, was immediately con- 
densed by the cold cylinder and water of condensation, and 
this continued until the cylinder became again heated up to 
212°, to which point the whole cylinder should be heated 



JAMES WATT. 75 

before the ascent could be completed. Here, then, was an 
obvious and an extensive cause of the waste of heat. At 
every descent of the piston, the cylinder should be cooled 
below 100°; and at every ascent it should be again heated 
to 212°. It, therefore, became a question whether the force 
gained by the increased perfection of the vacuum was ade- 
quate to the waste of fuel in producing the vacuum ; and it 
was found, on the whole, more profitable not to cool the 
cylinder" to so low a temperature, and consequently to work 
with a very imperfect vacuum, and a diminished power. 

Watt, therefore, found the engine involved in this dilem- 
ma: either much or little condensation-water must be used. 
If much were used, the vacuum would be perfect; but then 
the cylinder would be cooled, and would entail an extensive 
waste of fuel in heating it. If little were used, a vapour 
would remain, which would resist the descent of the piston, 
and rob the atmosphere of a part of its power. The great 
problem then pressed itself on his attention, to condense the 
steam without cooling the cylinder. 

From the small quantity of water in the form of steam 
which filled the cylinder, and the large quantity of injected 
water to which this communicated heat, Watt was led to 
inquire what proportion the bulk of water in the liquid state 
bore to its bulk in the vaporous state; and also what propor- 
tion subsisted between the heat which it contained in these 
two states. He found by experiment that a cubic inch of 
water formed about a cubic foot of steam ; and that the cubic 
foot of steam contained as much heat as would raise a cubic 
inch of water to about 1000°. (15.) This gave him some 
surprise, as the thermometer indicated the same temperature, 
212°, for both the steam andthe water from which it was 
raised. What then became of all the additional heat which 
was contained in the steam, and not indicated by the ther- 
mometer? Watt concluded that this heat must be in' some 
way engaged in maintaining the water in its new form. 

Struck with the singularity of this circumstance, he com- 



76 THE STEAM ENGINE. 

municated it to Dr. Black, who then explained to Watt his 
doctrine of latent heat, which he had been teaching for a 
short time before that, but of which Watt had not previously 
heard; and thus, says Watt, " I stumbled upon one of the 
material facts on which that theory is founded." 

(47.) Watt now gave his whole mind to the discovery of 
a method of "condensing the steam without cooling the 
cylinder." The idea occurred to him of providing a vessel 
separate from the cylinder, in which a constant vacuum 
might be sustained. If a communication could be opened 
between the cylinder and this vessel, the steam, by its. ex- 
pansive property, would rush from the cylinder to this 
vessel, where, being exposed to cold, it would be imme- 
diately condensed, the cylinder meanwhile being sustained 
at the temperature of 212°. 

This happy conception formed the first step of that bril- 
liant career which has immortalized the name of Watt, and 
which has spread his fame to the very skirts of civilization. 
He states, that the moment the notion of " separate conden- 
sation" struck him, all the other details of his improved 
engine followed in rapid and immediate succession, so that 
in the course of a day his invention was so complete that 
he proceeded to submit it to experiment. 

His first notion was, as we have stated, to provide a 
separate vessel, called a condenser, having a pipe or tube 
communicating with the cylinder. This condenser he pro- 
posed to keep cold by being immersed in a cistern of cold 
water, and by providing a jet of cold water to play within 
it. When the communication with the cylinder is opened, 
the steam, rushing into the condenser, is immediately con- 
densed by the jet and the cold surface. But here a difficulty 
presented itself, viz. how to dispose of the condensing water, 
and condensed steam, which would collect in the bottom of 
the condenser. But besides this, a quantity of air or per- 
manent uncondensible gas would collect from various 
sources. Water in its ordinary state always holds more or 



JAMES WATT. 77 

less air in combination with it: the air thus combined with 
the water in the boiler passes through the tubes and cylinder 
with the steam, and would collect in the condenser. Air 
also would enter in combination with the condensing water, 
which would be set free by the heat it would receive from 
admixture with the steam. The air proceeding from these 
sources would, as Watt foresaw, accumulate in the condenser, 
even though the water might be withdrawn from "it, and 
would at length resist the descent of the piston. To remedy 
this he proposed to form a communication between the 
bottom of the condenser and c. pump which he called the 
air pump, so that the water and air which might be col- 
lected in the condenser would be drawn off; and it was 
easy to see how this pump-could be worked by the machine 
itself. This constituted the second great step in the inven- 
tion. 

To make it air-tight in the cylinder, it had been found 
necessary to keep a quantity of water supplied above the 
piston. In the present case, any of this water which might 
escape through the piston, or between it and the cylinder, 
would boil, the cylinder being kept at 212°; and would 
thus, by the steam it would produce, -vitiate the vacuum. 
To avoid this inconvenience, Watt proposed to lubricate the 
piston, and keep it air-tight, by employing melted wax and 
tallow. 

Another inconvenience was still to be removed. On the 
descent of the piston, the air which must then enter the 
cylinder would lower its temperature; so that upon the next 
ascent, some of the steam which would enter it would be 
condensed, and hence would arise a source of Waste. To re- 
move this difficulty, Watt proposed to close the top of the 
cylinder altogether by an air-tight and steam-tight cover, 
allowing the piston-rod to play through a hole furnished 
with a stuffing-box, and to press down the piston by steam 
instead of the atmosphere. 

This was the third step in this great invention, and one 



78 THE STEAM ENGINE. 

which totally changed the character of the machine. It now 
became really a steam engine in every sense; for the pres- 
sure above the piston was the elastic force - of steam, and the 
vacuum below it wasproduced by the condensation of steam; 
so that steam was used both directly and indirectly as a 
moving power; whereas, in the atmospheric engine, the 
indirect force of steam only was used, being adopted merely 
as an ea§3>- method of producing a vacuum. 

The last difficulty respecting the economy of heat which 
remained to be removed, was the circutnstaneeof the cylin- 
der being liable to be cooled on the external surface by the 
atmosphere. To obviate this, he first proposed casing the 
cylinder in wood, that being a substance which conducted 
heat slowly. Hesubsequently, however, adopted a different 
method, and inclosed one cylinder within another, leaving a 
space between them, which he kept constantly supplied with 
steam. Thus the inner cylinder was kept continually at 
the temperature of the steam which surrounded it. The 
outer cylinder was called the jacket.* 

(48.) Watt computed that in the atmospheric engine three 
times as much heat was wasted in heating the cylinder, &c. 
as was spent in useful effect. And, as by the improvements 
proposed by him nearly all this waste was removed, he con- 
templated, and afterwards actually effected, a saving of three 
fourths of the fuel. 

. The honour due to Watt for his discoveries is enhanced 
by the difficulties under which he laboured from contracted 
circumstances at the time he made them. He relates, that 
when he was endeavouring to determine the heat consumed 
in the production of steam, his means did not permit him to 
use an efficient and proper apparatus, which would have 
been attended with expense; and it was by experiments made 

* It is a remarkable circumstance, that Watt used the same means for 
keeping the cylinder hot as Newcomen used in his earlier engines to 
cool it. (38.) 



JAMES WATT. 79 

with apothecaries' phials, that he discovered the property 
already mentioned, which was one of the facts on which the 
'doctrine of latent heat was founded. 

A large share of the merit of Watt's discoveries has, by 
some writers, been attributed to Dr. Black, to whose in- 
structions on the subject of latent heat it is said that Watt 
owed the knowledge of those facts which led to his improve- 
ments. Such, however, was not the case ; and the mistake 
arose chiefly from some passages respecting Watt in the 
works of Dr. Robison, in one of which he states that Watt 
had been a pitpil and intimate friend of Dr. Black; and that 
he attended two courses of his lectures at college in Glasgow;. 
Such, however, was not the case: for "Unfortunately for 
me," says Watt in a letter to Dr. Brewster, " the necessary 
avocations of my business prevented me from attending his 
or any other lectures at college. In further noticing Dr. 
Black's opinion, that his fortunate observation of what hap- 
pens in the formation and condensation of elastic vapour 
' has contributed in no inconsiderable degree to the public 
good, by suggesting to my friend Mr. Watt of Birmingham, 
then of Glasgow, his improvements on the steam-engine,' it 
is very painful for me to controvert any opinion or assertion 
of my revered friend; yet, in the present case, I find it ne- 
cessary to say, that he appears to me to have fallen into an 
error. These improvements proceeded upon the established 
fact, that steam was condensed by the contact of cold bodies, 
and the later known one, that water boiled at heats below 
100°, and consequently that a vacuum could not be obtained 
unless the cylinder and its contents were cooled every stroke 
below the heat." 



so 



CHAPTER V. 

watt's single-acting- steam engine. 

Expansive Principle applied. — Failure of Roebuck, and Partnership with 
Bolton. — Patent extended to 1800. — Counter.— Difficulties in getting 
the Engines into use. 

. (49.) The first machine in which Watt realised the con- 
ceptions which we mentioned in the last chapter, is that 
which was afterwards called his Single-acting Steam En- 
gine. We shall now describe the working apparatus in this 
machine. 

The cylinder is represented at c (fig. 12.) — in which the 
piston p moves steam-tight. It is closed at the top, and the 
piston rod being very accurately turned, runs in a steam- 
tight collar b furnished with a stuffing-box, and constantly 
supplied with melted tallow or wax. Through a funnel in 
the top of the cylinder, melted grease flows upon the piston 
so as to maintain it steam-tight. Two boxes a a, contain- 
ing the valves for admitting and withdrawing the steam, 
connected by a tube of communication t, are attached to the 
cylinder ; the aetion of these valves will be presently de- 
scribed. Below the cylinder, placed in a cistern of cold 
water, is a close cylindrical vessel d, called the condenser, 
communicating with the cylinder by a tube t', leading to 
the lower valve-box a.* In the side of this condenser is in- 
serted a tube, the inner end of which is pierced with holes 
like the rose of a watering-pot; and a cock e in the cold cis- 
tern-is placed on the outside^ through which, when open, 
the water passing, rises in a jet on the inside. 

The tube s, which conducts steam from the boiler, enters 
the top of the upper valve-box at f. Immediately under it 



WATT'S SINfciJL.U-ACTrNGr STEAM ENGINE. 81 

is placed a valve g, which is opened and closed by a lever 
or rod g'. This valve, when open, admits steam to the top 
of the piston, and also to the tube t, which communicates 
between the two valve-boxes, and when closed suspends the 
admission of steam. There are two valves in the lower box, 
one H in the top worked by the lever h', and one i in the 
bottom worked by the lever i'. The valve h, when open, 
admits steam to pass from the cylinder above the piston, by 
the tube t, to the cylinder below the piston, the valve i be- 
ing supposed in this case to be closed. This valve i, when 
open, (the valve h being closed), admits steam to pass from 
below the cylinder through t' to the condenser. This steam, 
entering the condenser, meets the jet, admitted to play. by 
the valve e, and is condensed. 

The valve g is called the tipper steam-valve ; h, lower 
steam-valve; i, the exhausting valve; and e, the con- 
densing valve. Let us now consider how these valves must 
be worked in order to produce the alternate ascent and de- 
scent of the piston. 

It is in the first place necessary that all the air which. fills 
the cylinder, tubes, and condenser, should be expelled. T<? 
accomplish this it is only necessary to open at once the vaVes 
g, h, and i. The steam then rushing from f through the 
valve G will pass into the upper part of the cylinder, and 
through the tube t and the valve h into the lovy^r part, and 
also through the valve i into the condenser. After the steam 
ceases to be condensed by the cold of the^apparatus, it will 
rush out mixed with air through the y/we m, which opens 
outwards; and this will continue ut*il all the air has been 
expelled, and the apparatus filled>ith*pure steam. Then 
suppose all the valves again closX The cylinder both above 
and below the piston is fillet with steam ; and the steam 
which filled the condenser feing cooled by the cold surface, 
a vacuum has been produced in that vessel. 

The apparatus being in this state, let the upper steam 
valve g, the exhausting valve i, and the condensing valve e 

11 



g2 THE STEAM EiVGrl-NE. 

be opened. Steam will thus be admitted through g to press 
on the top of the piston; and this steam will be prevented 
from circulating to the lower part of the cylinder by the 
lower steam-valve h being closed. Also the steam which 
filled the cylinder below the piston rushes through the open 
exhausting valve i to the condenser, where it meets the jet 
allowed to play by the open condensing valve e. It is thus 
instantly condensed, and a vacuum is left in the cylinder 
below the piston. Into this vacuum the piston is pressed 
without resistance by the steam which is admitted through g. 
When the piston has thus been forced to the bottom of the 
cylinder, let the three valves g, i, and e, which were before 
opened, be closed, and let the lower steam-valve h be opened. 
The effects of this change are easily perceived. By closing 
the upper steam-valve g, the further admission of steam to 
the apparatus is stopped. By closing the exhausting valve i, 
all transmission of steam from the cylinder to the condenser 
is stopped. Thus the steam which is in the cylinder, valve- 
boxes, and tubes is shut up in them, and no more admitted, 
nor any allowed to escape. By closing the condensing valve 
"«:, the play of the jet in the condenser is suspended. 

"Previously to opening the valve h, the steam contained 
in tht apparatus was confined to the part of the cylinder 
above ttys piston and the tube t and the valve-box a. But 
on opening this valve, the steam is allowed to circulate 
above and beUw the piston; and in fact through every part 
included between the upper steam valve g, and the exhaust- 
ing valve i. The ?ame steam circulating on both sides, the 
piston is thus equally pressed upwards and downwards. 

In this case there is to force tending to retain the piston 
at the bottom of the cylinder except its own weight. Its 
ascent is produced in the sam* manner as the ascent of the 
piston in the atmospheric engin t . The piston-rod is con- 
nected by chains g to the arch-he^d of the beam, and the 
weight of the pump-rod k, or any other counterpoise acting 



watt's single-acting steam engine. S3 

on the chains suspended from the other arch-head, draws the 
piston to the top of the cylinder. 

When the piston has arrived at the top of the cylinder, 
suppose the three valves g, i, and e to be again opened, and 
h closed. Steam passes from the steam-pipe r through the 
upper steam r valve g to the top of the piston, and at the same 
time the steam which filled the cylinder below the piston is 
drawn off through the open exhausting valve I into the con- 
denser, where it is condensed by the jet allowed to play by 
the open condensing valve e. The pressure of the steam 
above the piston then forces it without resistance into the 
vacuum below it, and so the process is continued. 

It should be remembered, that of the four valves necessary 
to work the piston, three are to be opened the moment the 
piston reaches the top of the cylinder, and the fourth is to be 
closed; and on the piston arriving at the bottom of the cylin- 
der, these three are to be closed and the fourth opened. The 
three valves which are thus opened and closed together are 
the upper steam-valve, the exhausting-valve, and the con- 
densing-valve. The lower steam-valve is to be opened at 
the same instant that these are closed, and vice versa. The 
manner of working these valves we shall describe hereafter. 

The process which has just been described, if continued 
for anj'- considerable number of reciprocations of the piston, 
would be attended with two very obvious effects which 
would obstruct and finally destroy the action of the machine. 
First, the condensing water and condensed steam would 
collect in the condenser d, and fill it; and- secondly, the 
water in the cistern in which the condenser is placed would 
gradually become heated, until at last it would not be cold 
enough to condense the steam when introduced in the jet. 
Besides this, it will be recollected that water boils in a 
vacuum at a very low temperature (17); and, therefore, the 
hot water collected in the bottom of the condenser would 
produce steam which, risipg into the cylinder through the 
exhausting valve, would resist the descent oi the piston, and 



84 THE STEAM ENGINE. 

counteract the effects of the steam above it. A further dis- 
advantage arises from the air or other permanently elastic 
fluid which enters in combination with the water, both in 
the boiler and condensing jet, and which is disengaged by 
its own elasticity. 

To remove these difficulties, a pump is placed near the 
condenser communicating with it by a valve m, which opens 
from the condenser into the pump. In this pump is placed 
.a piston which moves air-tight, and in which there is a valve 
n, which opens upwards. Now suppose the piston at the 
bottom of the pump. As it rises, since the valve in it opens 
upwards, no air can pass down through it, and consequently 
it leaves a vacuum below it. The water and any air which 
may be collected in the condenser open the valve m, and 
pass into the lower part of the pump from which they can- 
not return in consequence of the valve m opening outwards. 
On the descent of the pump-piston, the fluids which occupy 
the lower part of the pump, force open the piston-valve n; 
and passing through it, get above the piston, from which 
their return is prevented by the valve n. In the next ascent, 
the piston lifts these fluids to the top of the pump, whence 
they are discharged through a conduit into a small cistern b 
by a valve k which opens outwards. The water which is 
thus collected in b is heated by the condensed steam, and is 
reserved in b, which is called the hot well for feeding the 
boiler, which is effected by means which we shall presently 
explain. The pump which draws off the hot water and air 
from the condenser is called the air-pump. 

(50.) We have not yet explained the manner in which the 
valves and the air-pump piston are worked. The rod q of 
the latter is connected with the working beam, and the 
pump is therefore wrought by the engine itself. It is not 
very material to which arm of the beam it is attached. If 
it be on the same side of the centre of the beam with the 
cylinder, it rises and falls with the steam-piston ; but if it 
be on the opposite side, the pump-piston rises when the 



WATTS SINGLE-ACTING STEAM ENGINE. S5 

steam-piston falls, and vice versa. In the single-engine 
there are some advantages in the latter arrangement. As 
the steam-piston descends, the steam rushes into the conden- 
ser, and the jet is playing ; and this, therefore, is the most 
favourable time for drawing out the water and condensed 
steam from the condenser by the ascent of the pump-piston, 
since by this means the descent of the steam-piston is assist- 
ed ; an effect which would not be produced if the steam- 
piston and pump-piston descended together. 

With respect to the method of opening and closing the 
valves, it is evident that the three valves which are simul- 
taneously opened and closed may be so connected as to be 
worked by the same lever. This lever may be struck by a 
pin fixed upon the rod q of the air-pump, so that when the 
pistons have arrived at the top of the cylinders the pin strikes 
the lever and opens the three valves. A catch or detent is 
provided for keeping them open during the descent of the 
piston, from which they are disengaged in a similar manner 
on the arrival of the piston at the bottom of the cylinder, and 
they close by their own weight. 

In exactly the same way the lower steam-valve is opened 
on the arrival of the piston at the bottom of the cylinder, 
and closed on its arrival at the top by the action of a pin 
placed on the piston-rod of the air-pump. 

(51.) Soon after the invention of these engines, Watt 
found that in some instances inconvenience arose from the 
too rapid motion of the steam-piston at the end of its stroke, 
owing to its being moved with an accelerated motion. 
This was owing to the uniform action of the steam-pressure 
upon it: for upon first putting it in motion at the top of the 
cylinder, the motion was comparatively slow; but from the 
continuance of the same pressure the velocity with which the 
piston descended was continually increasing, until it reached 
the bottom of the cylinder, where it acquired its greatest 
velocity. To prevent this, and to render the descent as 
nearly as possible uniform, it was proposed to cut off the 



86 THE STEAM ENGINE. 

steam before the descent was completed, so that the remain- 
der might be effected merely by the expansion of the steam 
which was admitted to the cylinder. To accomplish this, 
he contrived, by means of a pin on the rod of the air-pump, 
to close the upper steam-valve when the steam-piston had 
completed one-third of its entire descent, and to keep it 
closed during the remainder of the descent, and until the 
piston again reached the top of the cylinder. By this ar- 
rangement the steam pressed the piston with its full force 
through one-third of the descent, and thus put it into motion; 
during the other, two thirds the steam thus admitted acted 
merely by its expansive force, which became less in exactly 
the same proportion as the space given to it by the descent 
of the piston increased. Thus, during the last two thirds of 
the descent the piston is urged by a gradually decreasing 
force, which in practice was found just sufficient to sustain 
in the piston a uniform velocity. 

(52.) We have already mentioned the difficulty arising 
from the water in the cistern, in which the condenser and 
air-pump are placed, becoming heated, and the condensation 
therefore being imperfect. To prevent this, a waste-pipe is 
placed in this cistern, from which the water is continually 
discharged, and a pump l (called the cold-water pump) is 
worked by the engine itself, which raises a supply of cold 
water and sends it through a pipe in a constant stream into 
the cold cistern. The waste-pipe, through which the water 
flows from the cistern, is placed near the top of it, since the 
heated water, being lighter than the cold, remains on the 
top. Thus the heated water is continually flowing off, and 
a constant stream of cold water supplied. The piston-rod 
of the cold water pump is attached to the beam (by which 
it is worked), usually on the opposite side from the cylin- 
der. 

Another pump o (called the hot-water pump) enters the 
hot well b ; and raising the water from it, forces it through 
a tube to the boiler for the purpose of feeding it. The 



watt's single-acting steam engine. 87 

manner in which this is effected will be more particularly 
described hereafter. A part of the heat which would other- 
wise be lost, is thus restored to the boiler to assist in the 
production of fresh steam. We may consider a portion of 
the heat to be in this manner circulating continually 
through the machine. It proceeds from the boiler in steam, 
works the piston, passes into the condenser, and is recon- 
verted into hot water; thence it is passed to the hot well, 
from whence it is pumped back into the boiler, and is again 
converted into steam, and so proceeds in constant circula- 
tion. 

From what has been described, it appears that there are 
four pistons attached to the great beam and worked by the 
piston of the steam-cylinder. On the same side of the cen- 
tre with the cylinder is the piston-rod of the air-pump, and 
on the opposite side are the piston-rods of the hot-water 
pump and the cold-water pump; and lastly, at the extremi- 
ty of the beam opposite to that at which the steam-piston 
works, is the piston of the pump to be wrought by the en- 
gine. 

(53.) The position of these piston-rods with respect to the 
centre of the beam depends on the play necessary to be 
given to the piston. If the play of the piston be short, its 
rod will be attached to the beam near the centre ; and if 
longer, more remote from the centre. The. cylinder of the 
air-pump is commonly half the. length of the steam-cylinder, 
and its piston-rod is attached to the beam at the point exact- 
ly in the middle between the end of the beam and the centre. 
The hot-water pump not being required to raise a conside- 
rable quantity of water, its piston requires but little play, 
and is therefore placed near the centre of the beam, the pis- 
ton-rod of the cold-water pump being farther from the 
centre. 

(54.) It appears to have been about the year 1763, that 
Watt made these improvements in the steam engine, and 
constructed a model which fully realized his expectations. 



8-8 THE STEAM ENGINE. 

Either from want of influence or the fear of prejudice and 
opposition, he did not make known his discovery or attempt 
to secure it by a patent at that time. Having adopted the 
profession of a land surveyor, his business brought him into 
communication with Dr. Roebuck, at that time extensively 
engaged in mining speculations, who possessed some com- 
mand of capital, and was of a very enterprising disposition. 
By Roebuck's assistance and countenance, Watt erected an 
engine of the new construction at a coal mine on the estate 
of the Duke of Hamilton, at Kinneil near Burrowstoness. 
This engine being a kind of experimental one, was improved, 
from time to tune as circumstances suggested, until it reached 
considerable perfection. While it was being erected, Watt 
in conjunction with Roebuck applied for and obtained a 
patent to secure the property in the invention. This patent 
was enrolled in 1769, six years after Watt invented the im- 
proved engine. 

Watt was now preparing to manufacture the new engines 
on an extensive scale, when his partner Roebuck suffered a 
considerable loss by the failure of a mining speculation in 
which he had engaged, and became involved in embarrass- 
ments, so as to be unable to make the pecuniary advances 
necessary to carry Watt's designs into execution. Again 
disappointed, and harassed by the difficulties which he had 
to encounter, Watt was about to relinquish the further pro- 
secution of his plans, when Mr. Matthew Bolton, a gentle- 
man who had established a factory at Birmingham a short 
time before, made proposals to purchase Dr. Roebuck's share 
in the patent, in which he succeeded ; and in 1773, Watt 
entered into partnership with Bolton. 

His situation was now; completely changed. Bolton was 
not only a man of extensive capital, but also of considerable 
personal influence, and had a disposition which led him, 
from taste, to undertakings which were great and difficult, 
and which he prosecuted with the most unremitting ardency 
and spirit. " Mr. Watt," says Play fair, " was studious and 



WATTS STNfiT.rc-AfiTTNft STEAM ENGINE. 89 

reserved, keeping aloof from the world ; while Mr. Bolton 
was a man of address, delighting in society, active, and mix- 
ing with people of all ranks with great freedom, and with- 
out ceremony. Had Mr. Watt searched all Europe, he 
probably would not have found another person so fitted to 
bring his invention before the public, in a manner worthy 
of its merit and importance ; and although of most opposite 
habits, it fortunately so happened that no two men evermore 
cordially agreed in their intercourse with "each other." 

The delay in the progress of the manufacture of engines 
occasioned by the failure of Dr. Roebuck was such, that 
Watt found that the duration of his patent would probably 
expire before he would even be reimbursed the necessary 
expenses attending the various arrangements for the manu- 
facture of the engines. He therefore, with the advice and 
influence of Bolton, Roebuck, and other friends, in 1775, 
applied to parliament for an extension of the terms of his 
patent, which was granted for 25 years from the date of his 
application, so that his exclusive privilege should expire in 
1800. 

An engine was now erected at Soho (the name of Bolton's 
factory) as a specimen for the- examination of mining specu- 
lators, and the engines were beginning to come into demand. 
The. manner in which Watt chose to receive remuneration 
from those who used his engines was as remarkable for its 
ingenuity as for its fairness and liberality. He required 
that one-third of the saving of coals effected by his engines, 
compared with the atmospheric engines hitherto used, should 
be paid to him, leaving the benefit of the other two-thirds 
to the public. Accurate experiments were made to ascer- 
tain the saving of coals; and as the amount of this saving in 
each engine depended on the length of time it was worked, 
or rather on the number of descents of the piston, Watt in- 
vented a very ingenious method of determining this. The 
vibrations of the great working beam were made to commu- 
nicate with a train of wheelwork, in the same way as those 

12 



90 THE STEAM ENGINE. 

of a pendulum communicate with the work of a clock. Each 
vibration of the beam moved one tooth of a small wheel, 
and the motion was communicated to a hand or index, which 
moved on a kind of graduated plate like the dial plate of a 
clock. The position of this hand marked the number of vi- 
brations of the beam. This apparatus, which was called the 
counter, was locked up and secured by two different keys, 
one of which was kept by the proprietor, and the other by 
Bolton and Watt, whose agents went round periodically to 
examine the engines, when the counters were opened by 
both parties and examined, and the number of vibrations of 
the beam determined, and the value of the patent third 
found.* 

Nowithstanding the manifest superiority of these engines 
over the old atmospheric engines ; yet such were the influ- 
ence of prejudice and the dislike of what is new, that Watt 
found great difficulties in getting them into general use. The 
comparative first cost also probably operated against them ; 
for it was necessary that all the parts should be executed 
with great accuracy, which entailed proportionally increased 
expense. In many instances they felt themselves obliged to 
induce the proprietors of the old atmospheric engines to re- 
place them by the new ones, by allowing them in exchange 
an exorbitant price for the old engines ; and in some cases 
fhey were induced to erect engines at their own expense, 
upon an agreement that they should only be paid if the en- 
gines were found to fulfil the expectations, and brought the 
advantages which they promised. It appeared since, that 
Bolton and Watt had actually expended a sum of nearly 
50,000/. on these engines before they began to receive any 
return. When we contemplate the immense advantages 

* The extent of the saving in fuel may be judged from this : that for 
three engines erected at Chacewater mine in Cornwall, it was agreed by 
the proprietors that they would compound for the patent third at 2400/. 
per annum ; so that the whole saving must have exceeded 7200/. per 
annum. 



DOUBLE-ACTING STEAM ENGINE. 91 

which the commercial interests of the country have gained 
by the improvements in the steam engine, we cannot but 
look back with disgust at the influence of that fatal preju- 
dice which opposes the progress of improvement under the 
pretence of resisting innovation. It would be a problem of 
curious calculation to determine what would have been lost 
to the resources of this country, if chance had not united the 
genius of such a "man as Watt with the spirit, enterprise, and 
capital, of such a man -as Bolton! The result would reflect 
little credit on those "who think novelty alone a sufficient 
reason for opposition. 



CHAPTER VI. 



DOUBLE-ACTING STEAM ENGINE. 

The Single -Acting Engine unfit to impel Machinery. — Various contri- 
vances to adapt it to this purpose. — Double-Cylinder. — Double-Acting 
Cylinder. — Various mode- of connecting the Piston with the Beam. — 
Rack and Sector. — Double Chain. — Parallel Motion. — Crank. — Sun 
and Planet Motion. — Fly Wheel. — Governor. 

In the atmospheric engine of Newcomen, and in the 
improved steam engine of Watt, described in the last 
chapter, the action of the moving power is an intermitting 
one. While the piston descends, the moving power is in 
action, but its action is suspended during the ascent. Thus 
the opposite or working end of the beam can only be applied 
in cases where a lifting power is required. This action is 
quite suitable to the purposes of pumping, which was the 
chief or only object to which the steam engine had hitherto 
been applied. In a more extended application of the ma- 
chine, this intermission of the moving power and its action 



92 THE STEAM ENGINE. 

taking place only in one direction would be inadmissible. 
To drive the machinery generally employed in manufactures 
a constant and uniform force is required; and to render the 
steam engine available for this purpose, it would be necessary 
that the beam should be driven by the moving power as well 
in its ascent as in its descent. 

When Watt first conceived the notion of extending the 
application of the engine to manufactures generally, he pro- 
posed to accomplish this double action upon the beam by 
placing a steam cylinder under each end of it, so that while 
each piston would be ascending, and not impelled by the 
steam, the other would be descending, being urged down- 
wards by the steam above it acting against the vacuum be- 
low. Thus, the power acting on each during the time when 
its action on the other would be suspended, a constant force 
would be exerted upon the beam, and the uniformity of the 
motion would be produced by making both cylinders com- 
municate with the same boiler, so that both pistons would 
be driven by steam of the same pressure. . One condenser 
might also be used for both cylinders, so that a similar 
vacuum would be produced under each. 

This arrangement, ho\vever,*was soon laid aside for one 
much more simple and obvious. This consisted in the pro- 
duction of exactly the same effect by a single cylinder in 
which steam was introduced alternately above and below 
the piston, being at the same time withdrawn by the con- 
denser at the opposite side. Thus the piston being at the 
top of the cylinder, steam is introduced from the boiler 
above it, while the steam in the cylinder below it is drawn 
off by the condenser. The piston, therefore, is pressed from 
above into the vacuum below, and descends to the bottom of 
the cylinder. Having arrived there, the top of the cylinder 
is cut off from all communication with the boiler; and, on 
the other hand, a communication is opened between it and 
the condenser. The steam which has pressed the piston 
down is therefore dvawn off by the condenser, while a com- 



DOUBLE- ACTING- STEAM ENGINE. 93 

munication is opened between the boiler and the bottom of 
the cylinder, so that steam is admitted below the piston: the 
piston, thus pressed from below into the vacuum above, 
ascends, and in the same way the alternate motion is con- 
tinued. Such is the principle of what is called the Double- 
acting Steam Engine, in contradistinction to that described 
in the last chapter, in which the steam acts only above 1 the 
piston while a vacuum is produced below it. 

It is evident that, in the arragement now described, the 
condenser, must be in constant action: while the piston is 
descending the condenser must draw off the steam below it, 
and while it is ascending, it must draw off the steam above 
it. As steam, therefore, must be. constantly drawn into the 
condenser, the jet of cold water which condenses the steam 
must be kept constantly playing. This jet, therefore, will 
not be worked by the valve alternately opening and closing, 
as in the single engine, but will be worked by a cock, the 
opening of which will be adjusted according to the quantity 
of cold water necessary to condense the steam. When the 
steam is used at a low pressure, and, therefore, in a less 
compressed state, less condensing water would be necessary 
than when it is used at a higher pressure and in a more com- 
pressed state. In the one case, therefore, the condensing 
cock would be less open than in the other. Again, the 
quantity of condensing water must vary with the speed of 
the engine, because the greater the speed of the engine, the 
more rapidly will the steam flow from the cylinder into the 
condenser ; and, as the same quantity of steam requires the 
same quantity of condensing water, the supply of the con- 
densing water must be proportional to the speed of the en- 
gine. In the double-acting engine, then, the jet cock is re- 
gulated by a lever or index which moves upon a graduated 
arch, and which is regulated by the engineer according to 
the manner in which the engine works. 

This change in the action of the steam Upon the piston 
rendered it necessary to make a corresponding change in 



94 THE STEAM ENGINE. 

the mechanism by which the piston-rod was connected with 
the beam. In the single acting engine, the piston-rod pulled 
the end of the beam down during the descent, and was pulled 
up by it in the ascent. The connection by which this action 
was transmitted between the beam and piston was, as we 

. have seen, a flexible chain passing from the end of the piston- 
and playing upon the arch head of the beam. ' Now, whete 
the mechanical action to be transmitted is a pull, and not a 

push, a flexible chain, or cord, or strap, is always sufficient; 
but if a push or thrust is required to be transmitted, then 
the flexibility of the medium of mechanical communication 
afforded by a chain, renders it inapplicable. In the double- 
acting engine, during the descent, the piston-rod still pulls 
the beam down, and so far a chain connecting the piston-rod 
with, the beam would be sufficient to"transmit the action of 
the one to the other; but in the ascent the beam no longer 
pulls up the piston-rod, but is pushed up by it. A chain 
from the piston-rod to the arch head, as described in the 
single acting engine, would fail to transmit this force. If 
such a chain were used with the double engine, where there is 
no counter weight on the opposite end of the beam, the conse- 
quence would be, that in the ascent of the piston the chain 
would slacken, and the beam would still remain depressed. 
It is therefore necessary that some other mechanical connec- 
tion be contrived between the piston-rod and the beam, of 
such a nature that in the descent the piston-rod may pull the 
beam down, and may push it up in the ascent. 

Watt first proposed to effect this by attaching to the end 
of the piston-rod a straight rack, faced with teeth, which 
should work in corresponding teeth raised on the arch head 
of the beam as represented in fig. 13. ,If his improved steam 
engines required.no further precision of operation and con- 
struction than the atmospheric engines, this might have been 
sufficient; but in these engines it was indispensably necessary 

. that the piston-rod should be guided with a smooth and even 
motion through the stuffing box in the top of the cylinder, 



DOUBLE-ACTING STEAM ENGINE. 95 

otherwise any shake or irregularity would cause it to work 
loose iri the stuffing box, and either to admit the air, or to 
let the steam escape. In fact, it was necessary to turn these 
piston-rods very accurately in the lathe, so that they may 
work with sufficient precision in the cylinder. Under these 
circumstances, the motion of the rack and toothed arch head 
were inadmissible, since it was impossible by such means to 
impart to the piston-rod that smooth and equable motion 
which was requisite. Another contrivance which occurred 
to Watt was, to attach to the top of the piston-rod a bar 
which should extend above the beam, and to use two chains 
or straps, one extending from the top of the bar to the lower 
end of the arch head, and the other from the bottom of the. 
bar to the upper end of the arch head. By such means the 
latter strap would pull the beam down when the piston 
would descend, and the former would pull the beam up- when 
the piston would ascend. These contrivances, however, 
were superseded by the celebrated mechanism, since called 
the Parallel Motion, one of the most ingenious mechanical 
combinations connected with the history of the steam 
engine. 

It will be observed that the object was to connect by some 
inflexible means the end of the piston-rod with the extremity 
of the beam, and so to contrive the mechanism, that while 
the end of the beam would move alternately up and down 
in a circle, the end of the piston-rod connected with the 
beam should move exactly up and down in a straight line. 
If the end of the piston-rod were fastened upon the end of 
the beam by a pivot without any other connexion, it is evi- 
dent that, being moved up and down in the arch of a circle, 
it would be bent to the left and the right alternately, and 
would consequently either be broken, or would work loose 
in the stuffing box. Instead of connecting the end of the 
rod immediately with the end of the beam by a pivot, Watt 
proposed to connect them by certain moveable, rods so 



96 THE STEAM ENGINE. 

arranged that, as the end of the heam wou-ld move up and 
down in the circular arch, the rods would so accommodate 
themselves to that motion, that the end connected with the 
piston-rod should not be disturbed from its rectilinear 
course. 

To accomplish .this, he conceived the notion of connecting 
three rods in the following manner : — A b' and c d (fig. 14.), 
are two rods or levers turning on fixed pivots or centres at 
A and c. A third rod, b d, is connected with them by pivots 
placed at their extremities, b and d, and the lengths of the 
rods are so adjusted that when A b and c d are horizontal, 
b d shall be perpendicular or vertical, and that a b and c d 
shall be of equal lengths. Now, let a pencil be imagined to 
be placed at p, exactly in the middle of the rod b d : if the 
rod a b be caused to move up and down like the beam of the 
steam engine in the arch represented in the figure, it is clear, 
from the mode of their connexion, that the rod c d will be 
moved up and down in the other arch. Now Watt con- 
ceived that, under such circumstances, the pencil p would be 
moved up and down in a perpendicular straight line. 

However difficult the first conception of this mechanism 
may have been, it is easy to perceive why the desired effect 
will be produced by it. When the rod a b rises to the up- 
per extremity of the arch, the point b departs a little to the 
right; at the same time, the point d is moved a little to the 
left. Now the extremities of the rod b d being thus at the 
same time, carried slightly in opposite directions, the pencil 
in the middle of it will ascend directly upwards ; the one 
extremity of the rod having a tendency to draw it as much 
to the right as the other has to draw it to the left. In the 
same manner, when the rod a b moves to the lower extre- 
tremit}' of the arch, the rod c D.will be likewise moved to 
the lower extremity of its arch. The point b is thus trans- 
ferred a little to the right, and the point d to the left; and, 
for the same reason as before, the point p in the middle will 



DOUBLE-ACTING STEAM ENGINE. 97 

move neither to the right nor to the left, but straight down- 
wards.* 

Now Watt conceived that his object would be attained if 
he could contrive to make the beam perform the part of a b 
in fig. 14., and to connect with it other two rods, c" d and 
D b, attaching the end of the piston to the middle of the rod 
d b. The practical application of this principle required 
some modification, but is as elegant as the notion itself is in- 
genious. 

The apparatus adopted for carrying it into effect is repre- 
sented on the arm which works the piston in fig. 15. The 
beam, moving on its axis c, every point in its arm moves in 
the arc of a circle of which c is the centre. Let b be the 
point which divides the arm a c into equal parts, a b and 
b c; and let d e be a straight rod equal in length to c b, and 
playing on the fixed centre or pivot d. The end e of this 
rod is connected by a straight bar, e b, with the point b, by 
pivots at b and e on which the rod b e plays freely. If the 
beam be supposed to move alternately on its axis c, the point 
b will move up and down in a circular arc, of which c is the 
centre, and at the same time the point e will move in an 
equal circular arc round the point d as a centre. According 
to what we have just explained, the middle point p of the 
rod b e will move up and down in a straight line. 

Also, let a rod, a g, equal in length to b e, be attached 
to the end a of the beam by a pivot on which it moves freely, 
and let its extremity g be connected with e by a rod, g e, 
equal in length to A b, and playing on pivots at g and e. 

By this arrangement the joint a g being always parallel 

* In a strict mathematical sense, the path of the point p is a curve of 
a high order, but in the play which is given to it in the application used 
in the steam engine, it describes only a part of its entire locus ; and this 
part extending equally on each side of a point of inflection, its radius of 
curvature is infinite, so that, in practice, the deviation from a straight 
line, when proper proportions are observed in the rods, and too great a 
play not given to them, is insignificant. 

13 



98 THE STEAM ENGINE. 

to b e, the three points c, a, and g will be in circumstances 
precisely similar to the points c, b, and f, except that the 
system c a g will be on a scale of double the magnitude of 
c b f: c a being twice c b, and a g twice b f, it is clear, 
then, that whatever course the point f may follow, the point 
g must follow a similar line,* but will move twice as fast. 
But, since the point f has been already shown to move up 
and down in a straight line, the point g must also move up 
and down in a straight line, but of double the length. t 

By this arrangement the pistons of both the steam cylin- 
der and air-pump are worked 5 the rod of the latter being 
attached to the point f, and that of the former to the point g. 

This beautiful contrivance, which is incontestibly one of 
the happiest mechanical inventions of Watt, affords an ex- 
ample with what facility the mind of a mere mechanician 
can perceive, as it were instinctively, a result to obtain 
which by strict reasoning would require a very complicated 
mathematical analysis. Watt, when asked, by persons 
whose admiration was justly excited by this invention, to 
what process of reasoning he could trace back his discovery, 
replied that he was aware of none; that the conception flash- 
ed upon his mind without previous investigation, and so as 
to excite in himself surprise at the perfection of its action ; 
and that on looking at it for the first time, he experienced 
all that pleasurable sense of novelty which arises from the 
first contemplation of the results of the invention of others. 

* It is, in fact, the principle of the pantograph. The points c, f, and 
g evidently he in the same straight line, since en: ca;: b f : a g, and 
the latter lines are parallel. Taking c as the common pole of the loci of 
the points r g, the radius vector of the one will always be twice the cor- 
responding radius vector of the other ; and therefore these curves are 
similar, similarly placed, and parallel. Hence, by the last note, the point 
g must move in a line differing imperceptibly from a right line. 

f It is not necessary that the rods, forming the parallel motion, should 
have the proportions which we have assigned to them. There are various 
proportions which answer the purpose, and which will be seen by refer- 
ence to practical works on the steam engine. 



DOUBLE-ACTING STEAM ENGINE. 99 

This and the other inventions of Watt seem to have hecn 
the pure creations of his natural genius, very little assisted 
by the results of practice, and not at all by the light of edu- 
cation. It does not even appear that he was a dexterous 
mechanic; for he never assisted in the construction of the 
first models of his own inventions. His dwelling-house 
was two miles from the factory, to which he never went 
more than once in a week, and then did not stay half an 
hour. 

(«) However beautiful and ingenious in principle the 
parallel motion may be, it has recently been shown in the 
United States that much simpler means are sufficient to sub- 
serve the same purpose. In the engines constructed recently, 
under the direction of Mr. R. L. Stevens, a substitute for 
the parallel motion has been introduced that performs the 
task equally well, and is much less complex. On the head 
of the piston-rod a bar is fixed, at right angles to it, and to 
the longitudinal section of the engine. The ends of this 
bar work in guides formed of two parallel and vertical bars 
of iron, by which the upper end of the piston-rod is con- 
strained to move in a straight line. The cross-bar that 
moves in the guides is connected with the end of the work- 
ing beam by an in-flexible bar, having a motion on two cir- 
cular gudgeons, one of which is in the working beam, the 
other in the cross-bar. This is therefore free to accommo- 
date itself to the changes in the respective position of the 
piston-rod and working beam, and yet transmits the power 
exerted by the steam Upon the former whether it be ascend- 
ing or descending, to the latter and through it to the other 
parts of the machine. — a. e. 

(b) The most improved form of Watt's engine was reach- 
ed by successive additions to the old atmospheric engine of 
Newcomen and Cawley. Hence, the working-beam, de- 
rived from the pump brake of that engine, always formed a 
part; and the parallel motion, or some equivalent contrivance 
was absolutely necessary. In many American engines, and 



100 THE STEAM ENGINE. 

particularly in those used in steam boats, the working beam 
no longer used for the purpose of transmitting motion to the 
machinery. This is effected by applying a bar, called the 
cross-head, at right angles to the upper ends of the piston- 
rod. The ends of the cross head work in iron guides, adapted 
to a gallows-frame of wood. On each side of the cylinder, 
connecting rods are applied, which take hold of the cranks 
of the shafts of the water-wheel. Two other connecting 
rods give motion to a short beam, which works the air and 
supply pumps. 

The working beam is also suppressed in engines which 
work horizontally. The connecting rod is in them merely 
a jointed prolongation of the piston rod, extending to the 
crank, whose axis lies in the same horizontal plane with and 
at right angles to the axis of the cylinder. — a. e. 

(55.) A perfect motion being thus obtained of conveying 
the alternate motion of the piston to the working beam, the 
use of a counterpoise to lift thepiston was discontinued, and 
the beam was made to balance itself exactly on its centre. 
The next end to be obtained was to adapt the reciprocating 
motion of the working end of the beam to machinery. The 
motion most generally useful for this purpose is one of 
continued rotation. The object, therefore, was by the 
alternate motion of the end of the beam to transmit to a 
shaft or axis a continued circular motion. In the first 
instance, Watt proposed effecting this by a crank, connected 
with the working end of the beam by a metal connector or 
rod. 

Let k be the centre or axis, or shaft by which motion is 
given to. the machinery, and to which rotation is to be im- 
parted by the beam c h. On the axle x, suppose a lever, 
k i, fixed, so that when k i is turned round the centre k, 
the wheel must be turned with it. Let a connector or rod, 
h i, be attached to the points h and i, playing freely on 
pivots or joints. As the end h is moved upwards and 
downwards, the lever k i is turned round the centre k, so 



DOUBLE-ACTING STEAM ENGINE. 101 

as to give a continued rotatory motion to the shaft which 
revolves on that centre. The different positions which the 
connector and lever k i assume in the different parts of a 
revolution are represented in fig, 16. 

(56.) This was the first method which occurred to Watt 
for producing a continued rotatory motion by means of the 
vibrating motion of the beam, and is the method now uni- 
versally used. A workman, however, from Mr. Watt's fac- 
tory, who was aware of the construction of a model of this, 
communicated the method to Mr. Washborough of Bristol, 
who anticipated Watt in taking out a patent; and although 
it was in his power to have disputed the patent, yet rather 
than be involved in litigation, he gave up the point, and 
contrived another way of producing the same effect, which 
he called the sun and planet wheel, and which he used 
until the expiration of Washborough's patent, when the 
crank Was resumed. 

The toothed wheel b (fig. 17.) is fixed on the end of the 
connector, so that it does not turn on its axis. The teeth of 
this wheel work in those of another wheel, A, which is the 
wheel to which rotation is to be imparted, and which is 
turned by the wheel b revolving round it, urged by the rod 
h i, which receives its motion from the working-beam. The 
wheel A is called the sun-wheel, and b the planet wheel, from 
the obvious resemblance to the motion of these bodies. 

This contrivance, although in the main inferior to the 
more simple one of the crank, is not without some advan- 
tages; among others, it gives to the sun-wheel double the 
velocity which would be communicated by the simple 
crank, for in the simple crank one revolution only on the 
axle is produced by one revolution of the crank, but in the 
sun and planet wheel two revolutions of the sun-wheel are 
produced by one of the planet-wheel; thus a double velocity 
is obtained from the same motion of the beam. This will 
be eviflent from considering that when the planet-wheel is 
in its highest position, its lowest tooth is engaged with the 



102 THE STEAM ENGINE. 

highest tooth of the sun-wheel; as the planet-wheel passes 
from the highest position, its teeth drive those of the sun- 
wheel before them, and when it eomes into the lowest posi- 
tion, the highest tooth of the planet-wheel is engaged with 
the lowest of the sun-wheel: but then half of the sun-wheel 
has rolled off the planet-wheel, and, therefore, the tooth 
which was engaged with it in its higher position, must now 
be distant from it by half the circumference of the wheel, 
and must therefore be again in the highest position, so that 
while the planet-wheel has been carried from the top 1o the 
bottom, the sun-wheel has made a complete revolution. A 
little reflection, however, on the nature of the motion, will 
render this plainer than any description can. This advan- 
tage of giving an increased velocity, may be obtained also 
by the simple crank, by placing toothed wheels on its axle. 
Independently of the greater expense attending the con- 
struction of the sun and planet wheel, its liability to go out 
of order, and the rapid wear of the teeth, and other objec- 
tions, rendered it decidedly inferior to the crank, which has 
now entirely superseded it. 

(58.) Whether the simple crank or the sun and planet 
wheel be used, there still remains a difficulty of a peculiar 
nature attending the continuance of the rotatory motion. 
There are two positions in which the engine can give no mo- 
tion whatever to the crank. These are when the end of the 
beam, the axle of the crank, and the pivot which joins the 
connector with the crank, are in the same straight line. 
This will be easily understood. Suppose the beam, con- 
nector, and crank to assume the position represented in fig. 
15. If steam urge the piston downwards, the point h and 
the connector h i will be drawn directly upwards. But it 
must be very evident that in the present situation of the 
connector h i, and the lever i k, the force which draws the 
point i in the direction i k can have no effect whatever in 
turning i k round the centre k, but will merely ejtert a 
pressure on the axle or pivots of the wheel. 



DOUBLE-ACTING STEAM ENGINE. 103 

Again, suppose the crank and connector to be in the position 
hIk (fig. 16.), the piston being consequently at the bottom 
of the cylinder. If steam now press the piston upivards, 
the pivot h and the connector h i will be pressed down- 
wards^ and this pressure will urge the crank i k in the 
direction i k. It is evident that such a force cannot turn 
the crank round the centre k, and can be attended with no 
other effect than a pressure on the axle or pivots of the 
wheel. 

Hence in these two positions, the engine can have no 
effect whatever in turning the crank. What, then, it may 
be asked, extricates the machine from this mechanical di- 
lemma in which it is placed twice in every revolution, on 
arriving at those positions in which the crank escapes the 
influence of the power ? There is a tendency in bodies, 
when once put in motion, to continue that motion until 
stopped by some opposing force, and this tendency carries 
the crank out of those two critical situations. The velocity 
which is given to it, while it is under the influence of the 
impelling force of the beam, is retained in a sufficient de- 
gree to carry it through that situation in which it is deserted 
by this impelling force. Although the rotatory motion in- 
tended to be produced by the crank is, therefore, not abso- 
lutely destroyed by this circumstance, yet it is rendered ex- 
tremely irregular, since, in passing through the two positions 
already described, where the machine loses its power over 
the crank, the motion will be very slow, and, in the posi- 
tions of the crank most remote from these, where the power 
of the beam upon it is greatest, the motion will be very 
quick. As the crank revolves from each of those positions 
where the power of the machine over it is greatest, to where 
that power is altogether lost, "it is continually diminished, 
so that, in fact, the crank is driven by a varying power, and 
therefore produces a varying motion. This will be easily 
understood by considering the successive positions of the 
crank and connector represented in fig. 16. 



104 THE STEAM ENGINE. 

This variable motion becomes particularly objectionable 
when the engine is employed to drive machinery. To re- 
move this defect, we have recourse to the property of bodies 
just mentioned, viz. their tendency to retain a motion which 
is communicated to them. A large metal wheel called afiy- 
ivheel is placed upon the axis of the t erank (fig. 15.), and is 
turned by it. The effect of this wheel is to equalize the mo- 
tion communicated by the action of the beam on the crank, 
that action being just sufficient to sustain in the fly-wheel 
a uniform velocity, and the tendency of this wheel to re- 
tain the velocity it receives, renders its rotation sufficiently 
uniform for all practical purposes. 

This uniformity of motion, however,- will only be pre- 
served on two conditions ; first, that the supply of steam 
from the boiler shall be uniform; and secondly, that the ma- 
chine have always the same resistance to overcome or be 
loaded equally. If the supply of steam from the boiler to 
the cylinder be increased, the motion of the piston will be. 
rendered more rapid, and, therefore, the revolution of the 
fly-wheel will also be more rapid, and, on the other hand, 
a diminished supply of steam will retard the fly-wheel. 
Again, if the resistance or load upon the engine be diminish- 
ed, the supply of sfeam remaining the same, the velocity 
will be increased, since a less resistance is opposed to the 
energy of the moving power ; and, on the other hand, if the 
resistance or load be increased, the speed will be diminished, 
since a greater resistance will be opposed to the same moving 
power. To insure a uniform velocity, in whatever manner 
the load or resistance may be changed, it is necessary to pro- 
portion the supply of steam to the resistance, so that, upon 
the least variation in the velocity, the supply of steam will 
be increased or diminished, so as to keep the engine going 
at the same rate. 

(59.) One of the most striking and elegant appendages of 
the steam engine is the apparatus contrived by Watt for 
effecting this purpose. An apparatus, called a regulator or 



•DOUBLE-ACTING STEAM ENGINE. 105 

governor, had been long known to mill-wrights for render- 
ing uniform the action of the stones in corn-mills, and was 
used generally in machinery. -Mr. Watt contrived a beau- 
tiful application of this apparatus for the regulation of the 
steam engine. In the pipe which conducts steam from the 
boiler to the cylinder he placed a thin circular plate, so that 
when placed with its face presented towards the length of 
the pipe, it nearly stopped it, and allowed little or no steam 
to pass to the cylinder, but when its edge was placed in the 
direction of the pipe, it offered no resistance whatever to the 
passage of the steam. This circular plate, called the throttle 
valve, was made to turn on. a diameter as an axis, passing 
consequently through the centre of the tube, and was worked 
by a lever'outside the tube. According to the position given 
to it, it would permit more or less steam to pass. If the 
valve be placed with its edge nearly in the direction of the 
tube, the supply of steam is abundant; if it be placed with its 
face nearly in the direction of the tube, the supply of steam 
is more limited, and it appears that, by the position given to 
this valve, the steam may be measured in any quantity to the 
cylinder. 

At first it was proposed that the engine-man should ad- 
just this valve with his hand; when the engine was observed 
to increase its speed too much, he would check the supply 
of steam by partially closing the valve; but if, on the other 
hand, the motion was too slow, he would open the valve 
and let in a more abundant supply of steam. Watt, how- 
ever, was not content with this, and desired to make the 
engine itself discharge this task with more steadiness and 
regularity than any attendant could, and for this purpose he 
applied the governor already alluded to. 

This apparatus is represented in fig. 15. ; e is a perpen- 
dicular shaft or axle to which a wheel, m, with a groove is 
attached. A strap or rope, which is rolled upon the axle of 
the fly-wheel, is passed round the groove in the wheel M,.in 
the same manner as the strap acts in a turning lathe. By 

14 



106 THE STEAM ENGINE. 

means of this strap the rotation of the fly-wheel will produce 
a rotation of the wheel m and the shaft l, and the speed of 
the one will always increase or diminish in the same pro- 
portion as the speed of the other, n, n are two heavy balls 
of metal placed at the ends of rods, which play on an axis 
fixed on the revolving shaft at o, and extend beyond the axis 
to q. q. Connected with these by joints at q ©.are two 
other rods, q r, which are attached to a broad ring of metal, 
moving freely up and down the revolving shaft. This ring 
is attached to a lever whose centre is s, and is connected by 
a series of levers with the throttle-valve t. When the speed 
of the fly-wheel is much increased, the spindle l is whirled 
round with considerable rapidity, and by their natural ten- 
dency* the balls n n fly from the centre. The levers which 
play on the axis o, by this motion, diverge from each other, 
and thereby depress the joints q q, and draw down the joints 
r, and with them the ring of metal which slides upon the 
spindle. By these means the end of the lever playing on s 
is depressed, and the end v raised, and the motion is trans- 
mitted to the throttle-valve, which is thereby partially closed, 
and the supply of steam to the cylinder cheeked. If, on the 
contrary, the velocity of the fly-wheel be diminished, the 
balls will fall towards the axis, and the opposite effects en- 
suing, the supply of steam will be increased, and the velocity 
restored. 

The peculiar beauty of this apparatus is, that in whatever 
position the balls settle themselves, the velocity with which 
the governor revolves must be the same,t and in this, in fact, 

• The centrifugal force. 

j- Strictly speaking-, this is only true when the divergence of the rods 
from the spindle is not very great, and, in practice, this divergence is 
never sufficient to render the above assertion untrue. This property of 
the conical pendulum arises from the circumstance of the centrifugal 
force, in this instance, varying as the radius of the circle in which the 
balls are moved; and when this is the case, as is well known, the perio- 
dic time is constant. The time of one revolution of the balls is equal to 
twice the time in which either ball, as a common pendulum, would 



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DOUBLE-ACTING STEAM ENGINE. 107 

consists its whole efficacy as a regulator. Its regulating 
power is limited, and it is only small changes of velocity 
that it will correct. It is evident that such a velocity as, on 
the one hand, would cause the balls to fly to the extremity 
of their play, or, on the other, would cause them to fall down 
on their rests, would not be influenced by the governor. 

We have thus described the principal parts of the double- 
acting steam engine. The valves and the methods of work- 
ing them have been reserved for the next chapter, as they 
admit of considerable variety, and will be better treated of 
separately. We have also reserved the consideration of the 
boiler, which is far from being the least interesting part of 
the modern steam engine, for a future chapter. 

vibrate on the centre, and as all its vibrations, though the arcs be un- 
equal, are equal in time, provided those arcs be small, so also is the 
periodic time of the revolving ball invariable. These observations, how- 
ever, only apply when the balls settle themselves steadily into a circular 
motion ; for while they are ascending they describe a spiral curve with 
double curvature, and the period will vary. This takes place during the 
momentary changes in the velocity of the engine. 



10S 



CHAPTER VII. 



DOUBLE-ACTING STEAM ENGINE 

[continued. ) 

On the Valves of the Double-Acting 1 Steam Engine. — Original Valves. — 
Spindle Valves. — Sliding Valve. — d Valve. — Four-Way Cock. 

(60.) The various improvements -described in the last 
chapter were secured to Watt by patent in the year 1782. 
The engine now acquired an enlarged sphere of action; for 
its dominion over manufactures was decided by the fly- 
wheel, crank, and governor. By means of these appen- 
dages, its motions were regulated with the most delicate 
precision; so that while it retained a power whose magni- 
tude was almost unlimited, that power was under as exact 
regulation as the motion of a time-piece. There is no 
species of manufacture, therefore, to which this machine is 
not applicable, from the power which spins the finest thread, 
or produces the most delieate web, to that which is necessary 
to elevate the most enormous weights, or overcome the most 
unlimited resistances. Although it be true, that in later 
times the steam engine has received many improvements, 
some of which are very creditable to the invention and 
talents of their projectors, yet it is undeniable that all its 
great and leading perfections, all those qualities by which it 
has produced such wonderful effects on the resources of 
these countries, by the extension of manufactures and com- 
merce, — those qualities by which its influence is felt and 
acknowledged in every part of the civilized globe, in in- 
creasing the happiness, in multiplying the enjoyments, and 
cheapening the pleasures of life, — that these qualities are 



DOUBLE-ACTING STEAM ENGINE. 109 

due to the predominating powers of one man, and that man 
one who possessed neither the influence of wealth, rank, nor 
education, to give that first impetus which is so often neces- 
sary to carry into circulation the earlier productions of 
genius. 

The method of working the valves of the double-acting 
steam engine, is a subject which has much exercised the 
ingenuity of engineers, and many elegant contrivances have 
been suggested, some of which we shall now proceed to 
describe. But even in this the invention of Watt has anti- 
cipated his successors; and the contrivances suggested by 
him are those which are now almost universally used. 

In order perfect!}' to comprehend the action of the several 
systems of valves which we are about to describe, it will be 
necessary distinctly to remember the manner in which the 
steam is to be communicated to the cylinder, and withdrawn 
from it. When the piston is at the top of the cylinder, the 
steam below it is to be drawn off to the condenser, and the 
steam from the boiler is to be admitted above it. Again, when 
it has arrived at the bottom of the cylinder, the steam above 
is to be drawn off to the condenser, and the steam from the 
boiler is to be admitted "below it. 

In the earlier engines constructed by Watt, this was ac- 
complished by four valves, which were opened and closed 
in pairs. Valve boxes were placed at the top and bottom 
of the cylinder, each of which communicated by tubes both 
with the steam-pipe from the boiler and the condenser. 
Each valve-box accordingly contained two valves, one to 
admit steam from the steam-pipe to the cylinder, and the 
other to allow that steam to pass into the condenser. Thus 
each valve-box contained a steam valve and an exhausting 
valve. The valves at the top of the cylinder are called the 
upper steam valve and the upper exhausting valve, and 
those at the bottom, the lower steam valve and the lower 
exhausting valve. In fig. 15. a' is the upper steam valve, 
which, when. open, admits steam above the. piston ; b' is the 



110 THE STEAM ENGINE. 

upper exhausting valve, which, when open, draws off the 
steam from the piston to the condenser, c' is the lower 
steam valve, which admits steam below the piston; and d, 
the lower exhausting valve, which draws off the steam from 
below the piston to the condenser. 

Now, suppose the piston to be at the top of the cylinder, 
the cylinder below it being filled with steam, which has just 
pressed it up. Let the upper steam valve a', and the lower 
exhausting valve d' be opened, and the other two valves 
closed. The steam which fills the cylinder below the pis- 
ton will immediately pass through the valve d' into the con- 
denser, and a vacuum will be produced below the piston. 
At the same time, steam is admitted from the steam-pipe 
through the valve a' above the piston, and its pressure will 
force the piston to the bottom of the cylinder. On the arri- 
val of the piston at the bottom of the cylinder, the upper 
steam valve a', and lower exhausting valve d', are closed ; 
and the lower steam valve c', and upper exhausting valve 
b' are opened. The steam which fills the cylinder above 
the piston now passes off through b' into the condenser, and 
leaves a vacuum above the piston. At the same time, steam 
from the boiler is admitted through the lower steam valve 
c', below the piston, so that it will press the piston to the 
top of the cylinder ; and so the process is continued. 

It appears, therefore, that the upper steam valve, and the 
lower exhausting valve, must be opened together, on the ar- 
rival of the piston at the top of the cylinder. To effect this, 
one lever, e', is made to communicate by jointed rods with 
both these valves, and this lever is moved by a pin placed 
on the piston-rod of the air-pump ; and such a position may 
be given to this pin as to produce the desired effect exactly 
at the proper moment of time. In like manner, another 
lever, p', communicates by jointed rods with the upper ex- 
hausting valve and lower steam valve, so as to open them 
and close them together ; and this lever, in like manner, 
is worked by a pin on the piston-rod of the air-pump. 



DOUDLE-ACTING STEAM ENGINE. Ill 

(61.) This method of connecting the valves, and working 
them, has been superseded by another, for which Mr. Mur- 
ray of Leeds obtained a patent, which was, however, set 
aside by Messrs. Bolton and Watt, who showed that they 
had previously practised it. This method is represented in 
figs. IS, 19. The stems of the valves are perpendicular, 
and move in steam-tight sockets in the top of the valve- 
boxes. The stem of the upper steam valve a is a tube through 
which the stem of the upper exhausting, valve b passes, and 
in which it moves steam-tight; both these stems moving 
steam-tight through the top of the valve-box. The lower 
steam valve c, and exhausting valve d, are similarly circum- 
stanced; the stem of -the former being a tube through which 
the stem of the latter passes. The stems of the upper steam 
valve and lower exhausting valve are then connected by a 
rod, e; and those of the upper exhausting valve and lower 
steam valve by another rod, f. These rods, therefore, are 
capable of moving the valves in pairs, when elevated and 
depressed. The motion which works the valves is, how- 
ever, not communicated by the rod of the air-pump, but is 
received from the axis of the fly-wheel. This axis works an 
apparatus called an eccentric; the principle which regulates 
the motion of this may be thus explained: — 

d e (figs. 20, 21.) is a circular metallic ring, the inner sur- 
face of which is perfectly smooth. This ring is connected 
with a shaft, r b, which communicates motion to the valves 
by levers which are attached to it at b. A circular metallic 
plate is fitted in the ring so as to be capable of turning within 
it, the surfaces of the ring and plate which are in contact 
being smooth and lubricated with oil or grease. This circu- 
lar plate revolves, but not on its centre. It turns on an axis 
c, at some distance from its centre a; the effect of which, evi- 
dently, is that the ring within which it is turned is moved 
alternately in opposite directions, and through a space equal 
to twice the distance (c a) of the axis of the circular plate 
from the common centre of it and the ring. The eccentric 



112 THE STEAM ENGINE. 

in its two extreme positions is represented in figs. 20, 21. 
The plate and ring d e are placed on the axis of the fly- 
wheel, or'on the axis of some other wheel which is worked 
by the fly-wheel. So that the motion of continued rotation 
in the fly-wheel is thus made to produce an alternate motion 
in a straight line in the shaft f b. This rod is made to com- 
municate by levers with the rods e and r (figs. 18, 19.), 
which work the valves in such a manner, that, when the 
eccentric is in the position fig. 20., one pair of valves are 
opened, and the other pair closed; and when it is brought to 
the position fig. 21., the other pair are opened and the for- 
mer closed and so on. It is by means of such an apparatus 
as this that the valves are worked almost universally at 
present. 

The piston being supposed to be at the top of the cylinder 
(fig. 18.), and the rod e raised, the valves a and d aie opened, 
and b and c closed. The steam enters from the steam-pipe 
at an aperture immediately above the valve a, and, passing 
through the open valve, enters the cylinder above the piston. 
At the same time, the steam which is below the piston, and 
which has just pressed it up, flows through the open valve 
d, and through a tube immediately under it to the condenser. 
A vacuum being thus produced below the piston, and steam 
pressure acting above it, it descends; and when it arrives at 
the bottom of the cylinder (fig. 19.) the rod r is drawn down, 
and the valves a and n fall into their seats, and at the same 
time the rod f is raised, and the valves b and c are opened. 
Steam is now admitted through an aperture above the valve 
c, and passes below the piston, while the steam above it 
passes through the open valve b into a tube immediately 
under it, which leads to the condenser. A vacuum being: 
thus produced above the piston, and steam pressure acting 
below it, the piston ascends, and thus the alternate ascent 
and' descent is continued by the motion communicated to 
the rods e f from the fly-wheel. 



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DOUBLE-ACTING STEAM ENGINE. 113 

(c) An improvement has been made in the United States 
in the mode of working the puppet valve. It consists in 
placing them by pairs in two different vertical planes in- 
stead of one. The rods then work through four separate 
stuffing boxes, and the necessity of making two of them hol- 
low cylinders is avoided. — a. e. 

(62.) There are various other contrivances for regulating 
the circulation of steam through the cylinder. In figs. 22, 
23. is represented a section of a slide valve suggested by Mr. 
Murray of Leeds. The steam-pipe from the boiler enters 
the valve-box d e at s. Curved passages, a a, b b, commu- 
nicate between this valve-box and the top and bottom of the 
cylinder; and a fourth passage leads to the tube c, which 
passes to the condenser. A sliding piece within the valve- 
box opens a communication alternately between each end of 
the cylinder and the tube c, which leads to the condenser. 
In the position of the apparatus in fig. 22. steam is passing 
from the steam-pipes, through the curved passage a a above 
the piston, and at the same time'the steam below the piston 
is passing through the passage b b into the tube c, and thence 
to the condenser. A vacuum is thus formed below the pis- 
ton, and steam is introduced above it. The piston, there- 
fore, descends; and when it arrives at the bottom of the cy- 
linder, the slide is moved into the position represented in 
fig. 23. Steam now passes from s through b b below the 
piston, and the steam above it passes through a a and c to 
the condenser. A vacuum is thus produced above the pis- 
ton, and steam pressure is introduced below it, and the pis- 
ton ascends; and in this way the motion is continued. 

The slide is moved by a lever, which is worked by the 
eccentric from the fly-wheel. 

(63.) Watt suggested a method of regulating the circula- 
tion of steam, which is called the d valve, from the resem- 
blance which the horizontal section of the valve has to the 
letter d. This method, which is very generally used, is re- 
presented in section in figs. 24, 25. Steam from the boiler 

15 






114 THE STEAM ENGINE. 

enters through s. A rod of metal connects two solid plugs, 
A b, which move steam-light in the passage d. In the posi- 
tion of the apparatus represented in fig. 24. the steam passes 
from s through the passage b, and enters the cylinder above 
the piston; while the steam below the piston passes through 
the open passage by the tube c to the condenser. A vacuum 
is thus formed below the piston, while the pressure .of steam 
is introduced above it, and it accordingly descends. When 
it has arrived at the bottom of the cylinder, the plugs a b 
are moved into the position in fig. 25. Steam now passing 
from s through d, enters rhe cylinder below the piston; 
while the steam which is above the piston, and has just 
pressed it down, passes through the open passage into the 
condenser. A vacuum is thus produced above the piston, 
and the steam pressure below forces it up. When it has 
arrived at the lop of the cylinder, the position of the plugs 
a b is again changed to that represented in fig. 24., and a 
similar effect to that already described is produced, and the 
piston is pressed down ; and so the process is continued. 

The plugs a b, and the rod which connects them, are 
moved up and down by proper levers, which receive their 
motion from the eccentric. 

This contrivance is frequently modified, by conducting 
the steam from above the piston to the condenser, through a 
tube in the plugs a b, and their connecting rod. In figs.-26, 
27. a tube passes through the plugs a b and the rod which 
joins them. In the position fig. 26. steam entering at s passes 
through the tube to the cylinder above the piston, while the 
steam below the piston passes through c into the condenser. 
A vacuum heing thus made below the piston, and steam 
pressing above it, it descends; and when it has arrived at the 
bottom of the cylinder, the position of the plugs A b and the 
tube is changed to that represented at fig. 27. The steam 
now entering at s passes to the cylinder below the piston, 
while the steam above the piston passes through c into the 
condenser. A vacuum is thus produced above the piston, 



DOUBLE-ACTING STEAM ENGINE. 115 

and steam pressure introduced below it, so that it ascends. 
When it lias arrived at the top of the cylinder, the plugs are 
moved into the position represented in fig. 20., and. similar 
effects being produced, the piston again descends: and so the 
motion is continued. 

The motion of the sliding lube may be produced as in the 
former contrivances, by the action of the eccentric. It is 
also sometimes done by a bracket fastened on the piston-rod 
of the air-pump. This bracket, in the descent of the piston, 
strikes a projection on the valve-rod, and drives it down; 
and in the ascent meets a similar projection, and raises it. 

(64.) Another method, worthy of notice for its elegance 
and simplicity, is the four-way cock. A section of this 
contrivance is given in figs. 28, 29.: c t s b are four pas- 
sages or tubes; s leads from the boiler, and introduces steam; 
c, opposite to it, leads to the condenser; t is a tube which 
communicates with the top of the cylinder; and b one which 
communicates with the bottom of the cylinder. These four 
tubes communicate with a cock, which is furnished with 
two curved passages, as represented in the figures; and these 
passages are so formed, that, according to the position given 
to the cock, they may be made to open a communication be- 
tween any two adjacent tubes' of the four just mentioned. 
When the cock is placed as in fig. 28. communication is 
opened between the steam-pipe and the top of the cylinder 
by one of the curved passages, and between the condenser 
and the bottom of the cylinder by the other curved passage. 
In this case the steam passes from below the piston to the 
condenser, leaving a vacuum under it, and steam is intro- 
duced from the boiler above the piston. The piston there- 
fore descends; and when it has arrived at the bottom of the 
cylinder, the position of the cock is changed to that repre- 
sented in fig. 29.. This change is made by turning the cock 
through one fourth of an entire revolution, which may be 
done by a lever moved by the eccentric, or by various other 
means. One of the curved passages in the cock now opens 



116 THE STEAM ENGINE. 

a communication between the steam-pipe and the bottom of 
the cylinder;'while the other opens a communication be- 
tween the condenser and the top of the cylinder. By these 
means, the steam from the boiler is introduced below the 
piston, while the steam above the piston is drawn off to the 
condenser. A vacuum being thus made above the piston,* 
and steam introduced below it, it ascends; and when it has 
arrived at the top of. the cylinder, the cock being moved 
back, it resumes the position in fig. 28. , and the same con- 
sequences ensue, the piston descends; and so the process is 
continued. In figs. 30, 31. the four-way cock with the pas- 
sages to the lop and bottom of the cylinder is represented 
on a larger scale. 

This beautiful contrivance is not of late invention. It was 
used by Papin, and is also described by Leupold in his Thea- 
trum Machinarum, a work published about the year 1720, 
in which an engine is described acting with steam of high 
pressure, on a principle which we shall describe in a subse- 
quent chapter. 

The four-way cock is liable to some practical objections. 
The quantity of steam which fills the tubes between the cock 
and the cylinder, is wasted every stroke. This objection, 
however, also applies to the sliding valve (figs. 22, 23.,) and 
to the sliding tube or d valves (figs. 24, 25, 26, 27.). In 
fact, it is applicable to every contrivance in which means 
of shutting off the steam are not placed at both lop and bot- 
tom of the cylinder. Besides this, however, the various pas- 
sages and tubes cannot be conveniently made large enough to 
supply steam in sufficient abundance; and consequently it 
becomes necessary to produce steam in the boiler of a more 
than ordinary strength to bear the attenuation which it suf- 
fers in its passage through so many narrow tubes. 

One of the greatest objections, however, to the use of the 
four-way cock, particularly in large engines, is its unequal 
wear. The parts of it near the passages having smaller sur- 
faces, become more affected by the friction, and in a short 



PI. "VII 



/■;■,/. 22. 






7\</. 24. 



F,<j. 25. 




7'Y'/- 26. 





/Jnnm fy//,r Jul/;,- 



J-Ingr. fy J J clcrMatrrich . 



BOILER AND ITS APPENDAGES. 117 

time the steam leaks between the cock and its case, and be- 
comes wasted, and tends to viliate the vacuum. These cocks 
are seldom used in condensing engines, except they be small 
engines, but are frequently adopted in high-pressure steam- 
engines; for in these the leakage is not of so much conse- 
quence, as will appear hereafter. 



CHAPTER VIII. 

BOILER AND ITS APPENDAGES. FURNACE. 

The Boiler and its Appendages. — Level Ganges. — Feeding Apparatus. 
— Steam Gauge. — Barometer Gauge. — Safety Valves. — Self-regulating 
Damper — Edelcrantz's Valve. — Furnace. — Self-consuming Furnace. — 
Brunton's Self-regulating Furnace. — Oldham's Modification. 

(65.) The regular action of a steam engine, as well as the 
economy of fuel, depends in a great degree on the construc- 
tion of the boiler or apparatus for generating the steam. The 
boiler may be conceived as a great magazine of steam for the 
use of the engine; and care must be taken not only that a 
sufficient quantity be always ready for the supply of the ma- 
chine, but also that it shall be of the proper quality; that is, 
that its pressure shall not exceed that which is required, 
nor fall short of it. Precautions should, therefore, be taken 
that the production of steam should be exactly proportioned 
to the work to be done, and that the steam so produced shall 
be admitted to the cylinder in the same proportion. 

To accomplish this, various contrivances, eminently re- 
markable for their ingenuity, have been resorted to, and 
which we shall now proceed to describe. 

(d) It may be premised that boiiers have been made of va- 
rious figures, each having its own peculiar advantages and de- 



118 THE STEAM ENGINE. 

fects. That which possesses the greatest degree of strength, is 
one of the shape of a cylinder. This form was originally in- 
troduced by Oliver Kvans, in the United States. It will have 
its entire superiority when the fire is made beneath it in a fur- 
nace of masonry. But this method is not applicable to steam- 
boats or locomotive engines. In these instances the weight of 
the separate furnace is an objection; when, therefore, this form 
is applied in them, the fire is usually made in a chamber of 
cylindric shape, within the boiler, and the smoke is convey- 
ed to the chimney by flues, which pass through the water. 
These flues have, in some cases, been reduced to the size of 
small tubes, and of this method an example will be found in 
a subsequent part of this work. — a. e. 

(66.) Different methods have been, from time to lime, 
suggested for indicating the level of the water in the boiler. 
We have already mentioned the two gauge-pipes used in the 
earlier steam engines (31.); and which are still generally con- 
tinued. There are, however, some other methods which 
merit our attention. 

A weight, f (fig. 32.), half immersed in the water in the 
boiler, is supported by a wire, which, passing steam-tight 
through a small hole in the top, is connected by a flexible 
string or chain passing over a wheel, w, with a counterpoise, 
A, which is just sufficient to balance f, when half immersed. 
If f be raised above the water, a being lighter, will no longer 
balance it, and f will descend, pulling up a, and turning the 
wheel w. If, on the other hand, f be plunged deeper in the 
water, a, will more than balance it, and will pull it up. So 
that the only position in which f and a will balance each 
other is when f is half immersed. The wheel w is so ad- 
justed, that when two pins, placed on its rim, are in the hori- 
zontal position, as in fig. 32., the water is at its proper level. 
Consequently it follows, that if the water rise above this level, 
the weight f is lifted, and a falls, so that the pins p p' come 
into the position in fig. 33. If, on the other hand, the level 
of the water falls, f falls and a rises, so that the pins p p' as- 



BOILER AND ITS APPENDAGES. 119 

sume the position in tig. 34. Thus, in general, the position 
of the pins p p' becomes an indication of the quantity of wa- 
ter in the boiler. 

Another method is to place a glass tube (fig. 35.) with one 
end, t, entering the boiler above the proper level, and the 
other end, V, entering it below the proper level. It must 
be evident that the water in the lube will always stand at 
the same level as the water in the boiler ; since the lower 
part has a free communication with that water, while the sur- 
face is submitted to the pressure of the same steam as the 
water in the boiler. This, and the last-mentioned gauge, 
have the advantage of addressing the eye of the engineer 
at once, without any adjustment; whereas the gauge cocks 
must be both opened, whenever the depth is to be ascer- 
tained. 

These gauges, however, require the frequent attention of 
the engine-man ; and it becomes desirable either to find 
some more effectual means of awakening that attention, or to 
render the supply of the boiler independent of any attention. 
In order to enforce the attention of the engine-man to re- 
plenish the boiler when partially exhausted by evaporation, 
a tube was sometimes inserted at ,the lowest level to which 
it was intended that the water should be permitted to fall. 
This tube was conducted from the boiler into the engine- 
house, where it terminated in a mouth-piece or whistle, so 
that whenever the water fell below the level at which this 
tube was inserted in the boiler, the steam would rush 
through it, and, issuing with great velocity at the mouth- 
piece, would summon the engineer to his duty with a call 
that would rouse him even from sleep. 

(67.) In the most effectual of these methods, the task of 
replenishing the boiler should still be executed by the en- 
gineer ; and the utmost that the boiler itself was made to do 
was to give due notice of the necessity for the supply of 
water. The consequence was, among other inconveni- 



120 THE STEAM ENGINE. 

ences, that the level of the water was subject to constant 
variation. 

To remedy this, a method has been invented by which 
the engine is made to feed its own boiler. The pipe g' 
(fig. 15.), which leads from the hot water pump h', termi- 
nates in a small cistern, c (fig. 36.), in which the water is 
received. In the bottom of this cistern a valve, v, is 
placed, which opens upwards, and communicates with a 
feed-pipe, which descends into the boiler below the level 
of the water in it. The stem of the valve v is connected 
wilh a lever turning on the centre d, and loaded with a 
weight, f, dipped in the water in the boiler in a manner 
similar to that described in fig. 32., and balanced by a 
counterpoise, a, in exactly the same way. When the level 
of the water in the boiler falls, the float f falls with it, and, 
pulling down the arm e of the lever, raises the valve v, and 
lets the water descend into the boiler from the cistern c. 
When the boiler has thus been replenished, and the level 
raised to its former place, r will again be raised, and the 
valve v closed by the weight a. In practice, however, the 
valve v adjusts itself by means of the effect of the water on 
the weight r, so as to permit the water from the feeding 
cistern c to flow in a continued stream, just sufficient in 
quantity to supply the consumption from evaporation, and 
to maintain the level of the water in the boiler constantly 
the same. 

By this singularly felicitous arrangement, the boiler is 
made to replenish itself, or, more properly speaking, it is 
made to receive such a supply as that it never wants reple- 
nishing, an effect which no effort of attention on the part of 
an engine-man could produce. But this is not the only 
good effect produced by this contrivance. A part of the 
steam which originally left the boiler, and having discharged 
its duty in moving the piston, was condensed and recon- 
verted into water, and lodged by the air-pump in the hot- 
well (47.), is here again restored to the source from which it 



BOILER AND ITS APPENDAGES. 121 

came, bringing back all the unconsumed portion of its heat 
preparatory to being once more put in circulation through 
the machine. 

The entire quantity of hot water pumped into the cistern 
c is not always required for the boiler. A waste-pipe may 
be provided for carrying off the surplus, which may be 
turned to any purpose for which it may be required; or.it 
may be discharged into a cistern to cool, preparatory to 
being restored to the cold cistern (fig. 12'.), in case water 
for the supply of that cistern be not sufficiently abundant. 

In cities and places in which it becomes an object to pre- 
vent the waste of water, the waste-pipes proceeding from the 
feed-cistern c (fig. 36.) and from the cold cistern containing 
the condenser and air-pump, may be conducted to a cistern 
A b (fig. 37.). Let c be the pipe from the feeding cistern, 
and d that from the cold cistern ; by these pipes the waste 
water, from both these cisterns is deposited in a b. In the 
bottom of a b is a valve v, opening upwards, connected with 
a float f. When the quantity of water collected in the cis- 
tern a b is such that the level rises considerably, the float f 
is raised, and lifts the valve v, and the water flows into the 
main pipe, which supplies water for working the engine: g 
is the cold water-pump for the supply of the cold cistern. 

This arrangement for saving the water discharged from 
the feeding and condensing cisterns has been adopted in the 
printing office of the Bank of Ireland, and a very considera- 
ble waste of water is thereby prevented. 

(68.) It is necessary to have a ready method of ascertain- 
ing at all times the strength of the steam which is used in 
working the engine. For this purpose a bent tube contain- 
ing mercury is inserted into some part of the apparatus 
which has free'communication with the steam. It is usually 
inserted in the jacket of the cylinder (44.). Let a b c (fig. 
38.) be such a tube. The pressure of the steam forces the 
mercury down in the leg a b, and up in the leg b c. If the 
mercury in both legs be at exactly the same level, the pres- 

16 



122 THE STEAM ENGINE. 

sure of the steam must be exactly equal to that of the atmo- 
sphere; because the steam pressure on the mercury in a b 
balances the atmospheric pressure on the mercury in b c. 
If, however, the level of the mercury in b c be above the 
level of the mercury in b a, the pressure of the steam will 
exceed that of the atmosphere. The excess of its pressure 
above that of the atmosphere may be found by observing 
the difference of the levels of the mercury in the tubes b c 
and b.a; allowing a pressure of one pound on each square 
inch for every two inches in the difference of the levels. 

If, on the contrary, the level of the mercury in b c should 
fall below its level in a b, the atmospheric pressure will ex- 
ceed that of the steam, and the degree or quantity of the 
excess may be ascertained exactly in the same way. 

If the tube be glass, the difference of levels of the mercury 
would be visible: but it is most commonly made of iron; 
and in order to ascertain the level, a thin wooden rod with 
a float is inserted in the open end of b c; so that the portiqn 
of the stick within the tube indicates the distance of the 
level of the mercury from its mouth. A bulb or cistern of 
mercury might be substituted for the leg a b, as in the 
common barometer. This instrument is called the steam- 
gauge. 

If the steam-gauge be used as a measure of the strength of 
the steam which presses on the piston, it ought to be on the 
same side of the throttle valve (which is regulated by the 
governor) as the cylinder; for if it were on the same side of 
the throttle valve with the boiler, it would not be affected by 
the changes which the steam may undergo in passing through 
the throttle valve, when partially closed by the agency of 
the governor. 

(69.) The force with which the piston is pressed depends 
on two things: 1°, the actual strength of the steam which 
presses on it; and 2°, on the actual strength of the vapour 
which resists it. For although the vacuum produced by 
the method of separate condensation be much more perfect 



TOILER AND ITS APPENDAGES. 123 

than what had been produced in the atmospheric engines, 
yet still some vapour of a small degree of elasticity is found 
to be raised from the hot water in the bottom of the con- 
denser before it can be extracted by the air-purnp. One of 
these pressures is indicated by the steam-gauge already de- 
scribed; but still, before we can estimate the force with 
which the piston descends, it is necessary to ascertain the 
force of the vapour which remains uncondensed, and resists 
the motion of the piston. Another gauge, called the baro- 
meter-gauge, is. provided for this purpose. A glass tube 
A b (fig. 39.), more than thirty inches long, and open at 
both ends, is placed in an upright or vertical position, having 
the lower end b immersed in a cistern of mercury c. To 
the upper end is attached a metal tube, which communicates 
with the condenser, in which a constant vacuum, or rather 
high degree of rarefaction, is sustained. The same vacuum 
must, therefore, exist in the tube a b, above the level of the 
mercury; and the atmospheric pressure on the surface of the 
mercury in the cistern c will force the mercury up in the 
tube A b, until the column which is suspended in it is equal 
to the difference between the atmospheric pressure and the 
pressure of the uncondensed steam. The difference between 
the column of mercury sustained in this instrument and in 
the common barometer will determine the strength of the 
uncondensed steam, allowing a force proportional to one 
pound per square inch for every two inches of mercury in 
the difference of the two columns. In a well-constructed 
engine, which is in good order, there is very little difference 
between the altitude in "the barometer-gauge and the common 
barometer. 

To compute the force with which the piston descends, 
thus becomes a very simple arithmetical process. First 
ascertain the difference of the levels of the mercury in the 
steam-gauge. This gives the excess of the steam pressure 
above the atmospheric pressure. Then find the height of 
the mercury in the barometer-gauge. This gives the excess 



124 THE STEAM ENGINE. 

of the atmospheric pressure above the unconclensed steam. 
Hence, if these two heights be. added together, we shall ob- 
tain the excess of the impelling force of the steam from the 
boiler on the one side of the piston, above the resistance of 
the uncondensed steam on the other side. This will give 
the effective impelling force. Now, if one pound be allowed 
for every two inches of mercury in the two columns just 
mentioned, we shall have the number of pounds of impelling 
pressure on every square inch of the piston. Then if the 
number of square inches in the section of the piston be found, 
and multiplied by the number of pounds on each square inch, 
the whole effective force with which it moves will be ob- 
tained. 

In the computation of the power of the engine, however, 
all this force, thus computed, is not to be allowed as the ef- 
fective working power. For it requires some force, and by 
no means an inconsiderable portion, to move the engine it- 
self, even when unloaded; all this, therefore, which is spent 
in overcoming friction, &c. is to be left, out of account, and 
only the balance set down as the effective working power. 

From what we have stated, it appears that in order to es- 
timate the effective force with which the piston is urged, it 
is necessary to refer to both the barometer and the steam- 
gauge. This double computation may be obviated by mak- 
ing one gauge serve both purposes. If the end c of the 
steam-gauge (fig. 38.) instead of communicating with the at- 
mosphere, were continued to the condenser, we should have 
the pressure of the steam, acting upon the mercury in the 
tube b A, and the pressure of the uncondensed vapour which 
resists the piston acting on the mercury in the tube b c. 
Hence the difference of the levels of the mercury in the 
tubes will at once indicate the difference between the force of 
the steam and that of the uncondensed vapour, which is the 
effective force with which the piston is urged. 

(70.) To secure the boiler from accidents arising from the 
steam becoming too strong, a safety valve is used, similar to 



BOILER AND ITS APPENDAGES. 125 

those described in Papin's steaift engine, loaded with a 
weight equal to the strength which the steam is intended to 
have above the atmospheric pressure; for it is found expe- 
dient, even in condensing engines, to use the steam of a pres- 
sure somewhat above that of the atmosphere. 

Besides this valve, another of the verj' opposite kind is 
sometimes used. Upon stopping the engine, and extinguish- 
ing the fire, it is found that the steam condensed within the 
boiler produces a vacuum; so that the atmosphere, pressing ' 
on the external surface of the boiler,, has a tendency to crush 
it. To prevent this, a safety valve is provided, which opens 
inwards, and which being forced open by the atmospheric 
pressure when a vacuum is produced within, the air rushes 
in, and a balance is obtained between the pressures within 
and without. 

■ (71.) We have already explained the manner in which the 
governor regulates the supply of steam from the boiler to the 
cylinder, proportioning the quantity to the work to be done, 
and thereby sustaining a uniform motion. Since, then, the 
consumption of steam in the engine is subject to variation, 
owing to the various quantities of work it may have to per- 
form, it is evident that the production of steam in the boiler 
should be subject to a proportional variation. For, other- 
wise, one of two effects would ensue : the boiler would either 
fail to supply the engine with steam, or steam would accu- 
mulate in the boiler, from being produced in too great abun- 
dance, and would escape at the safety valve, and thus be 
wasted. In order to vary the production of steam in propor- 
tion to the demands of the engine, it is necessary to increase 
or mitigate the furnace, as production is to be augmented or 
diminished. To effect this by any attention on the part of 
the engine-man would be impossible; but a most ingenious 
method has been contrived, of making the boiler regulate it- 
self in these respects. Let t (fig. 40.) be a tube inserted in 
the top of the boiler, and descending nearly to the bottom. 
The pressure of the steam on the surface of the water in 



126 THE STEAM ENGINE. 

the boiler forces water up in the tube t, until the differ- 
ence of the levels is equal to ihe difference between the pres- 
sure of the steam in the boiler and that of the atmosphere. 
A weight f, half immersed in the water in the tube, is sus- 
pended by a chain which passes over the wheels p p', and is 
balanced by a metal plate d, in the same manner as the float 
in fig. 32. is balanced by the weight A. The plate d passes 
through the mouth of the flue e, as it issues finally from the 
boiler ; so that when the plate d falls, it stops the flue and 
thereby suspends the draught of air through the furnace, 
mitigates the fire, and diminishes the production of steam. 
If, on the contrary, the plate d be drawn up. the draught is 
increased, the fire rendered more effective, and the produc- 
tion of steam in the boiler stimulated. Now suppose that 
the boiler is producing steam faster than the engine con- 
sumes it, either because the load on the engine has been di- 
minished, and therefore its consumption of steam proportion- 
ally diminished, or because the fire has become too intense. 
The consequence is, that the steam beginning to accumulate, 
will press upon the surface of the water in the boiler with 
increased force, and the water will rise in the tube t. The 
weight p will therefore be lifted, and the plalec will descend, 
stop the draught, mitigate the fire, and check the production 
of steam ; and it will continue so to do, until the production 
of steam becomes exactly equal to the demands of the en- 
gine. 

If, on the other hand, the production of steam be not equal 
to the wants of the machine, either because of the increased 
load, or the insufficiency of the fire, the steam in the boiler 
losing its elasticity, the surface of the water rises, not sus- 
taining a pressure sufficient to keep it at its wonted level. 
Therefore, the surface in the tube t falls, and the weight p 
falls, and the plate' d rises. The draught is thus increased, 
by opening the flue, and the fire rendered more intense; and 
thus the production of steam is stimulated, until it is suffi- 



FURNACE. 127 

ciently rapid for the purposes of the engine. This appara- 
tus is called the self-acting damper. 

(72.) It has been- proposed to connect this damper with 
the safety-valve invented by the Chevalier Eolelcrantz. A 
small brass cylinder is fixed to the boiler, and is fitted with 
a piston which moves in it, without much friction, and near- 
ly steam-tight. The cylinder is closed at top, having a hole 
through which the piston-rod plays ; so that the piston is 
thus prevented from being blown out of the cylinder by the 
steam. The side of the cylinder is pierced with small holes 
opening into the air, and placed at short distances above 
each other. Let the piston be loaded with a weight propor- 
tional to the pressure of the steam intended to be produced. 
When the steam has acquired a sufficient elasticity, the pis- 
ton will be lifted, and steam will escape through the first 
hole. If the production of steam be not too rapid, and that 
its pressure be not increasing, the piston will remain suspend- 
ed in this manner : but if it increase, the piston will be raised 
above the second hole, and it will continue to rise until the es-' 
cape of the steam through the holes is sufficient to render the 
weight of the piston a counterpoise for the steam. This 
safety valve is particularly well adapted to cases where steam 
of an exactly uniform pressure is required ; for the pressure 
must necessarily be always equal to the weight on the pis- 
ton. Thus, suppose the section of the piston be equal to a 
square inch ; if it be loaded with 10 lbs., including its own 
weight, the steam which will sustain it in any position in the 
cylinder, whether near the bottom or top, must always be 
exactly equal in pressure to 10 lbs. per inch. In this re- 
spect it resembles the quality already explained in the go- 
vernor, and renders the pressure of the steam uniform, ex- 
actly in the same manner as the governor renders the velo- 
city of the engine uniform. 

(73.) The economy of fuel depends, in a great degree, on 
the construction of the furnace, independently of the effects 
of the arrangements we have already described. 



128 THE STEAM ENGINE. 

The grate or fire-place of an ordinary furnace is placed 
under the boiler; and the atmospheric air passing through 
the ignited fuel, supplies sufficient bxy gen to support a large 
volume of flame, which is carried by the draught into a flue, 
which circulates twice or oftener round, the boiler, and in 
immediate contact with it, and finally issues into the chim- 
ney. Through this flue the flame circulates, so as to act on 
every part of the boiler near which the flue passes; and it is 
frequently not until it passes into the chimney, and some- 
times not until it leaves the chimney, that it ceases to exist 
in the state of flame. 

The dense black smoke which is observed to issue from 
the chimneys of furnaces is formed of a quantity of uncon- 
sumed fuel, and may be therefore considered as so much fuel 
wasted. Besides this, in large manufacturing towns, where 
a great number of furnaces are employed, it is found .that 
the quantity of smoke which thus becomes diffused through 
the atmosphere, renders it pernicious to the health, and de- 
structive to the comforts of the inhabitants. 

These circumstances have directed the attention of engi- 
neers to the discovery of means whereby this smoke or 
wasted fuel may be Consumed for the use of the engine itself, 
or for whatever use the furnace may be applied to. The 
most usual method of accomplishing this is by so arranging 
matters that fuel in a state of high combustion, and, there- 
fore, producing no smoke, shall be always kept on that part 
of the grate which is nearest to the mouth of the flue (and 
which we shall call the back) ; by this means the smoke 
which arises from the imperfectly ignited fuel which is 
nearer to the front of the grate must pass over the surface of 
the red fuel, before it enters the flue, and is thereby ignited, 
and passes in a state of flame into the flue. A passage called 
the feeding-mouth leads to the front of the grate, and both 
this passage and the grate are generally inclined at a small 
angle to the horizon, in order to facilitate the advance of the 
fuel according as its combustion proceeds. 



FURNACE. 129 

When fresh fuel for feeding the boiler is first introduced, 
it is merely laid in the feeding-mouth. Here it is exposed 
to the action of a part of the heat of the burning fuel on the 
grate, and undergoes, in some degree, the process of coking. 
The door of the feeding-mouth is furnished with small aper- 
tures for the admission of a stream of air, which carries the 
smoke evolved by the coking of the fresh fuel over the burn- 
ing fuel on the grate, by which this smoke is ignited, and 
becomes flame, and in this state enters the flue, and circu- 
lates round the boiler. When the furnace is to be fed, the 
door of the feeding-mouth is opened, and the fuel which had 
been laid in it, and partially coked, is forced upon the front 
part of the grate. At first, its combustion being imperfect, 
but proceeding rapidly, a dense black smoke arises from it. 
The current of air from the open door through the feeding- 
mouth carries this over the vividly burning fuel in the back 
part of the grate, by which the smoke being ignited, passes 
in a state of flame into the flue. When the furnace again re- 
quires feeding, every part of this fuel will be in a state of 
active combustion, and it is forced to the back part of the 
grate next the flue, preparatory to the introduction of more 
fuel from the feeding-mouth. 

The apertures in the door of the feeding-mouth are fur- 
nished with covers, so that the quantity of air admitted 
through them can be regulated by the workmen. The effi- 
ciency of these furnaces in a great degree depends on the 
judicious admission of the air through the feeding-mouth: 
for if less than the quantity necessary to support the com- 
bustion of the fuel be admitted, a part of the smoke will 
remain unconsumed; and if more than the proper quantity 
be admitted, it will defeat the effects of the fuel by cooling 
the boiler. If the process which we have just described be 
considered, it will not be difficult to perceive the total im- 
possibility in such a furnace of exactly regulating the draught 
of air, so that too much shall not pass at one time, and too- 
little at another. When the door is open to introduce fresh 

17 



130 THE STEAM ENGINE. 

fuel into the feeding-mouth, and advance that which occu- 
pied it upon the grate, the workman ceases to have any con- 
trol whatever over the draught of air; and even at other 
times when the door is closed, his discretion 'and attention 
cannot be depended on. The consequence is, that with 
these defects the proprietors of steam engines found, that in 
the place of economising the fuel, the use of these furnaces 
entailed on them such an increased expense that they were 
generally obliged to lay them aside. 

(74.) Mr. Brunton of Birmingham having turned his at- 
tention to the subject, has produced a furnace which seems 
to be free from the objections against those we have just 
mentioned. The advantages of his contrivance, as stated by 
himself, are as follow: — 

" First, I put the coal upon the grate by small quantities, 
and at very short intervals, say every two or three seconds. 
2dly, I so dispose of the coals upon the grate, that the 
smoke evolved must pass over that part of the grate upon 
which the coal is in full combustion, and is thereby con- 
sumed. 3dly, As the introduction of coal is uniform in 
short spaces of time, the introduction of air is also uniform, 
and requires no attention from the fireman. 

" As it respects economy: 1st, The coal is put upon the 
fire by an apparatus driven by the engine, and so contrived 
that the quantity of coal is proportioned to the quantity of 
work which the engine is performing, and the quantity of 
air admitted to consume the smoke is regulated in the same 
manner. 2dly, The fire door is never opened, excepting to 
clean the fire; the boiler of course is not exposed to that con- 
tinual irregularity of temperature which is unavoidable in 
the common furnace, and which is found exceedingly inju- 
rious to boilers. 3dly, The only attention required is to fill 
the coal receiver, every two or three hours, and clean the 
fire when necessary. 4thly, The coal is more completely 
consumed than by the common furnace, as all the effect of 
what is termed stirring up the fire (by which no inconsider- 



\ 



PI. TIU 



Tiff. la. 




FURNACE. 131 

able quantity of coal is passed into the ash-pit) is attained 
without moving the coal upon the grate." 

The fire-place is a circular grate placed on a vertical shaft 
in a horizontal position. It is capable of revolving, and is 
made to do so by the vertical shaft, which is turned by wheel- 
work, which is worked by the engine itself; or this shaft or 
spindle may be turned by a water-wheel, on which a stream 
of water is allowed to flow from a reservoir into which it is 
pumped by the power of the engine; and by regulating the 
quantity of water in the stream, the grate may be made to 
revolve with a greater or less speed. In that part of the 
boiler which is over the grate, there is an aperture, in which 
is placed a hopper, through which fuel is let down upon the 
grate at the rate of any quantity per minute that may be re- 
quired. The apparatus which admits the coals through this 
hopper is worked by the engine also, and by the same means 
as the grate is turned so that the grate revolves with a speed 
proportional to the rapidity with which the fuel is admitted 
through the hopper, and by this ingenious arrangement the 
fuel falls equally thick upon the grate. 

The supply of water which turns the wheel which works 
the grate and the machinery in the hopper, is regulated by 
a cock connected with the self-regulating damper; so that 
when the steam is being produced too fast, the supply of wa- 
ter will be diminished, and by that means the supply of fuel 
to the grate will be diminished, and the grate will revolve 
less rapidly: and when the steam is being produced too 
slowly for the demands of the engine, the contrary effects 
take place. In this way the fuel which is introduced into 
the furnace is exactly proportioned to the work which the 
engine has to perform. The hopper may be made large 
enough to hold coals for a day's work, so that the furnace 
requires no other attendance than to deposite coals in the hop- 
per each morning. 

The coals are let down from the hopper on the grate at 
that part which is most remote from the flue; and as they 



132 THE STEAM ENGINE. 

descend in very small quantities at a time, they are almost 
immediately ignited. But until their ignition is complete, 
a smoke will arise, which, passing to the flue over the 
vividly burning fuel, will be ignited. Air is admitted through 
proper apertures, and its quantity regulated by the damper 
in the same manner as the supply of fuel. 

The superiority of this beautiful invention over the com- 
mon smoke-consuming furnaces is very striking. Its prin- 
ciple of self-adjustment as to the supply of coals and atmo- 
spheric air, and the proportioning of these to the quantity of 
work to be performed by the engine, not only independent 
of human labour, but with a greater degree of accuracy than 
any human skill or attention could possibly effect, produces 
saving of expense, both in fuel and labour. 

(75.) Mr. Oldham, engineer to the Bank of Ireland, has 
proposed. another modification of the self-regulating furnace, 
which seems to possess several advantages, and evinces con- 
siderable ingenuity. 

He uses a slightly inclined grate, at the back or lower end 
of which is the flue, and at the front or higher end, the hop- 
per for admitting the coals. In the bottom or narrow end of 
the hopper is a moveable shelf, worked by the engine. Upon 
drawing back this shelf, a small quantity of fuel is allowed 
to descend upon a fixed shelf under it ; and upon the return 
of the moveable shelf, this fuel is protruded forward upon 
the grate. Every alternate bar of the grate is fixed, but the 
intermediate ones are connected with levers, by which they 
are moved alternately up and down.* The effect is, that 
the coals upon the-bars are continually stirred, and gradual- 
ly advanced by their own weight from the front of the grate, 
where they fall from the hopper, to the back, where they 

* Mr. Brunton used moveable bars in a furnace constructed by him be- 
fore he adopted the horizontal revolving grate. That plan, however, 
does not appear to have been as successful as the latter, as he has aban- 
doned it. Mr. Oldham states that his furnace has been in use for several 
years without any appearance of derangement in the mechanism, and with 
a considerable saving of fuel. « 



FURNACE. 133 

are deposited in the ash-pit. By the shape and construction 
of the bars, the air is conducted upwards between them, and 
rushes through the burning fuel, so as to act in the manner 
of a blowpipe, and the entire surface of the fire presents a 
sheet of flame. 

We cannot fail to be struck with the beauty of all these 
contrivances, by which the engine is made to regulate itself, 
and supply its own wants. It is in fact, all but alive. It 
was observed by Belidor, long before the steam engine reach- 
ed the perfection which it has now acquired, that it resem- 
bled an animal, and that no mere work of man ever ap- 
proached so near to actual life. Heat is the principle of its ex- 
istence. The boiler acts the part of the heart, from which its 
vivifying fluid rushes copiously through all the tubes, where 
having discharged the various functions of life, and deposited 
its heat in the proper places, it returns again to the source it 
sprung from, to be duly prepared for another circulation. 
The healthfulness of its action is indicated by the regularity 
of its pulsations ; it procures its own food by its own la- 
bour ; it selects those parts which are fit for its support, 
both as to quantity and quality; and has its natural evacua- 
tions, by which all the useless and innutritious parts are dis- 
charged. It frequently cures its own diseases, and corrects the 
irregularity of its own actions, exerting something like moral 
faculties. Without designing to carry on the analogy, Mr. 
Farey,- in speaking of the variations incident to the work 
performed by different steam engines, states some further 
particulars in which it may be curiously extended. "We 
must observe," says he, "that the variation in the perform- 
ance of different steam engines, which are constructed on 
the same principle, working under the same advantages, is 
the same as would be found in the produce of the labour of 
so many different horses or other animals when compared 
with their consumption of food ; for the effects of different 
steam engines will vary as much from small differences in 
the proportion of their parts, as the strength of animals from 



134 THE STEAM ENGINE. 

the vigour of their constitutions ; and again, there will be as 
great differences in the performance of the same engine 
when in good and bad order, from all the parts being tight 
and well oiled, so as to move with little friction, as there is 
in the labour of an animal from his being in good or bad 
health, or excessively fatigued : but in all these cases there 
will be a maximum which cannot be exceeded, and an ave- 
rage which we ought to expect to obtain." 



CHAPTER IX. 

DOUBLE-CYLINDER ENGINES. 
Hornblower's Engine. — Woolf 's Engine. — Cartwright's Engine. 

(76.) The expansive property of steam, of which Watt 
availed himself in his single engine by cutting off the supply 
of steam before the descent of the piston was completed, 
was applied in a peculiar manner by an engineer named 
Hornblower, about the year 1781, and at a later period 
by Woolf. Hornblower was the first who conceived the 
idea of working an engine with two cylinders of differ- 
ent sizes, by allowing the steam to flow freely from the boil- 
er until it fills the smaller cylinder, and then permitting it 
to expand into the greater one, employing it thus to press 
down two pistons in the manner which we shall presently 
describe. The condensing apparatus of Hornblower, as well 
as the other appendages of the engine, do not differ materi- 
ally from those of Watt ; so that it will be sufficient for our 
present purpose to explain the manner in which the steam is 
made to act in moving the piston. 

Let c, fig. 41., be the centre of the great working beam, 
carrying two arch heads, on which the chains of the pis- 



DOUBLE-CYLINDER ENGINES. 135 

Ion rods play. The distances of these arch heads from the 
centre c must be in the same proportion as the length of the 
cylinders, in order that the same play of the beam may cor- 
respond to the plays of both pistons. Let r be the steam- 
pipe from the boiler, and G a valve to admit the steam above 
the lesser piston, h is a tube by which a communication 
may be opened by the valve i between the top and bottom 
of the lesser cylinder b. k is a tube communicating, by the 
valve x,, between the bottom of the lesser cylinder b and the 
top of the greater cylinder a. m is a tube communicating, 
by the valve n, between the top and bottom of the greater 
cylinder a; and p a tube leading to the condenser by the ex- 
hausting valve o. 

At the commencement of the operation, suppose all the 
valves opened, and steam allowed to flow through the entire 
engine until the air be completely expelled, and then let all 
the valves be closed. To start the engine, let the exhaust- 
ing valve o and the steam valves g and l be opened, as in 
fig. 41. The steam will flow freely from the boiler, and 
press upon the lesser piston, and at the same time the steam 
below the greater piston will flow into the condenser, leav- 
ing a vacuum in the greater cylinder. The valve l being 
opened, the steam which is under the piston in the lesser 
cylinder will flow through k, and press on the greater pis- 
ton, which, having a vacuum beneath it, will consequently 
descend. At the commencement of the motion, the lesser 
piston is as much resisted by the steam below it as it is urged 
by the steam above it ; but after a part of the descent has 
been effected, the steam below the'lesser piston passing into 
the greater, expands into an increased space, and therefore 
loses its elastic force proportionally. The steam above the 
lesser piston retaining its full force by having a free commu- 
nication with the boiler by the valve g, the lesser piston will 
be urged by a force equal to the excess of the pressure of this 
steam above the diminished pressure of the expanded steam 
below it. As the pistons descend, the steam which is be- 



136 THE STEAM ENGINE. 

tween it continually increasing in its bulk, and therefore de- 
creasing in its pressure, from whence it follows, that the 
force which resists the lesser piston is continually decreasing, 
while that which presses it down remains the same, and 
therefore the effective force which impels it must be con- 
tinually increasing. 

On the other hand, the force which urges the greater pis- 
ton is continually decreasing, since there is a vacuum below 
it, and the steam which presses it is continually expanding 
into an increased bulk. 

Impelled in this way, let us suppose the pistons to have 
arrived at the bottoms of the cylinders, as in fig. 42., and let 
the valves g, l, and o be closed, and the valves i and n 
opened. No steam is allowed to flow from the boiler, g be- 
ing closed, nor any allowed to pass into the condenser, since 
o is closed, and all communications between the cylinders is 
stopped by closing l. By opening the valve i, a free com- 
munication is made between the top and bottom of the lesser 
piston through the tube h, so that the steam which presses 
above the lesser piston will exert the same pressure below it, 
and the piston is in a state of indifference. In the same 
manner the valve n being open, a free communication is 
made between the top and bottom of the greater piston, and 
the steam circulates above and below the piston, and leaves 
it free to rise. A counterpoise attached to the pump-rods in 
this case, draws up the piston, as in Watt's single engine; 
and when they arrive at the top, the valves i and n are 
closed, and g, l, and o opened, and the next descent of the 
pistons is produced in the manner already described, and so 
the process is continued. 

The valves are worked by the engine itself, by means 
similar to some of those already described. By computa- 
tion, we find the power of this engine to be nearly the same 
as a similar engine on Watt's expansive principle. It does 
not however appear, that any adequate advantage was gained 



DOUBLE-CYLINDER ENGINES. 137 

by this modification of the principle, since no engines of this 
construction are now made. 

(77.) The use of two cylinders was revived by Arthur 
Wool/, in 1804, who, in this and the succeeding year, ob- 
tained patents for the application of steam raised under a high 
pressure to double-cylinder engines. The specification of 
his patent states, that he has proved by experiment that 
steam raised under a safety-valve loaded with any given 
number of pounds upon the square inch, will, if allowed to 
expand into as many times its bulk as there are pounds of 
pressure on the square inch, have a pressure equal to that of 
the atmosphere. Thus, if the safety-valve be loaded with 
four pounds on the square inch, the steam, after expanding 
into four times its bulk, will have the atmospheric pressure. 
If it be loaded with 5, 6, or 10 lbs. on the square inch, it 
will have the atmospheric pressure when it has expanded 
into 5, 6, or 10 times its bulk, and so on. It was, however, 
understood in this case, that the vessel into which it was 
allowed to expand should have the same temperature as the 
steam before it expands. 

It is very unaccountable how a person of Mr. Woolf's ex- 
perience in the practical application of steam could be led 
into errors so gross as those involved in the averments of 
this patent; and it is still more unaccountable how the ex- 
periments could have been conducted which led him to con- 
clusions not only incompatible with all the established pro- 
perties of elastic fluids — properties which at that time were 
perfectly understood — but even involving in themselves 
palpable contradiction and absurdity. If it were admitted 
that every additional pound avoirdupois which should be 
placed, upon the safety-valre would enable steam, by its ex- 
pansion into a proportionally enlarged space, to attain a 
pressure equal to the atmosphere, the obvious consequence 
would be, that a physical relation would subsist between the 
atmospheric pressure and the pound avoirdupois! It is 
wonderful that it did not occur to Mr. Woolf, that, granting 

IS 



138 THE STEAM ENGINE. 

his principle to be true at any given place, it would neces- 
sarily be false at another place where the barometer would 
stand at a different height. Thus if the principle were true 
at the foot of a mountain, it would be false at the top of it; 
and if it were true in fair weather, it would be false in foul 
weather, since these circumstances would be attended by a 
change in the atmospheric pressure, without making any 
change in the pound avoirdupois.* 

The method by which Mr. Woolf proposed to apply the 
principle which he imagined himself to have discovered was 
by an arrangement of cylinders similar to those of Horn- 
blower, but having their magnitudes proportioned to the 
greater extent of expansion which he proposed to use. Two 
cylinders, like those of Hornblower, were placed under the 
working beam, having their piston rods at distances from 
the axis proportioned to the lengths of their respective 
strokes. The relative magnitudes of the cylinders a and b 
must be adjusted accbrding to the extent to which the prin- 
ciple of expansion is intended to be used. The valves c c' 
were placed at each end of the lesser cylinder in tubes com- 
municating with the boiler, so as to admit steam on each 
side of the lesser piston, and cut it off at pleasure. A tube, 
d', formed a communication between the upper end of the 
lesser and lower epd of the greater cylinder, which com- 
munication is opened and closed at pleasure by the valve e'. 
In like manner, the tube d forms a communication between 
the lower end of the lesser cylinder and the upper end of the 
greater, which may be opened and closed by the valve e. 
The top and bottom of the greater cylinder communicated 
with the condenser by valves f' y. 

Let us suppose that" the air is blown from the engine in 
the usual way, all the valves closed, and the engine ready to 

* It is strange that this absurdity has been repeatedly given as unques- 
tionable fact in various encyclopedias on the article " Steam Engine," 
as well as in by far the greater number of treatises expressly on the sub- 
ject. 



DOUBLE-CYLINDER ENGINES. 139 

start, the pistons being at the top of the cylinders. Open 
the valves c,e, and f. The steam which occupies the greater 
cylinder below the piston will now pass into the condenser 
through f, leaving a vacuum below the piston. The steam 
which is in the lesser cylinder below the piston will pass 
through d and open the valve e, and will press down the 
greater piston. The steam from the boiler will flow in at c, 
and press on the lesser piston. At first the whole motion 
will proceed from the pressure upon the greater piston, 
since the steam, both above and below the lesser piston, has 
the same pressure. But, as the pistons descend, the steam 
below the less passing into the g-reater cylinder, expands 
into a greater space, and consequently exerts a diminished 
pressure, and, therefore, the steam on the other side exerting 
an undiminished pressure, acquires an impelling force exactly 
equal to the pressure lost in the expansion of the steam be- 
tween the two pistons. Thus both pistons will be pressed 
to the bottoms of their respective cylinders. It will be ob- 
served that in the descent the greater piston is urged by a 
continually decreasing force, while the lesser is urged by 
continually increasing force. 

Upon the arri%l of the pistons at the bottoms of the 
cylinders, let the valves, c, e, f be closed, and c', e','f' be 
opened, as in fig. 44. The steam which is above the greater 
piston now flows through f' into the condenser, leaving the 
space above the piston a vacuum. The steam which is above 
the lesser piston passes through e' and d' below the greater, 
while the steam from the boiler is admitted through c' below 
the lesser piston. The pressure of the steam entering through 
e' below the greater piston, pressing on it against the vacuum 
above it, commences the ascent. In the mean time the steam 
above the lesser piston passing into the enlarged space of the 
greater cylinder, loses gradually its elastic force, so that the 
steam entering from the boiler at c' becomes in part effec- 
tive, and the ascent is completed under exactly the same 



140 THE STEAM ENGINE. 

circumstances as the descent, and in this way the process is 
continued. 

It is evident that the valves may he easily worked by the 
mechanism of the engine itself. 

In this arrangement the pistons ascend and descend to- 
gether, and their rods must consequently be attached to the 
beam at the same side of the centre. It is sometimes desi- 
rable that they should act on different sides of the centre of 
the beam, and consequently that one should ascend while 
the other descends. It is easy to arrange the valves so as 
to effect this. In fig. 45., the lesser piston is at the bottom 
of the cylinder, and the greater at the top. On opening the 
valves c', e', p', a vacuum is produced below the greater 
piston, and steam flows from the lesser cylinder, through e', 
above the greater piston, and presses it down. At the 
same time steam being admitted from the boiler through c' 
below the lesser piston, forces it up against the diminishing 
force of the steam above it, which expands into the greater 
cylinder. Thus as the greater piston descends the lesser 
ascends.' When each has traversed its cylinder, the valves 
c', e', f' being closed, a-nd c, e, f opened, the lesser piston 
will descend, and the greater ascend, and so on. 

(78.) The law according to which the elastic force of steam 
diminishes as it expands, of which Mr. Woolf appears to 
have been entirely ignorant, is precisely similar to the same 
property in air and other elastic fluids. If steam expands 
into twice or thrice its volume, it will lose its elastic force 
in precisely the same proportion as it enlarges its bulk; and 
therefore will have only a half or a third of its former pres- 
sure, supposing that as it expands its temperature is kept up. 
Although Mr. Woolf's patent contained the erroneous prin- 
ciple which we have noticed, yet, so far as his invention 
suggested the idea of employing steam at a very high pres- 
sure, and allowing it to expand in a much greater degree 
than was contemplated either by Watt or Hornblower, it 
became the means of effecting a considerable saving in fuel; 



DOUBLK-CYLINDER ENGINES. 141 

for engines used for pumping on a large scale, the steam 
being produced under a pressure of forty or fifty pounds or 
more upon the square inch, might be worked first through 
a small space with intense force, and the communication 
with the boiler being then cut off, it might be allowed, with 
great advantage, to expand through a very large space. 
Some double-cylinder engines upon this principle have been 
worked in Cornwall, with considerable economy. But the 
form in which the expansive principle, combined with high 
pressure, is now applied in the engines used for raising 
water from the mines, is that in which it was originally pro- 
posed by Watt. A single cylinder of considerable length 
is employed; the piston is driven through a small proportion 
of this length by steam, admitted from the boiler at a very 
intense pressure: the steam being then cut off, the piston is 
urged by the expansive force of the steam which has been 
admitted, and is by that means brought to the bottom of the 
cylinder. 

It is evident, under such circumstances, that the pressure 
of the steam admitted from the boiler must be much greater 
than the resistance opposed to the piston, and that the motion 
of the piston must, in the first instance, be accelerated and 
not uniform. I£ the piston moved from the commencement 
with a uniform motion, the pressure of the steam urging it 
must necessarily be exactly equal to the resistance opposed 
to it, and then cutting off the supply of steam from 'the boil- 
er, the piston could only continue its motion by inertia, the 
steam immediately becoming of less pressure than the resist- 
ance ; and after advancing through a very small space, the 
piston would recoil upon the steam, and come to a state of 
rest. The steam, however, at the moment it is cut off being 
of much greater pressure than the amount of resistance upon 
the piston, will continue to drive the piston forward, until 
by its expansion its force is so far diminished as to become 
equal to the resistance of the piston. From that point the 
impelling power of the steam will cease, and the piston will 



142 THE STEAM ENGINE. 

move forward by its inertia only. The point at which the 
steam is cut off should therefore be so regulated that it shall 
acquire a pressure equal to the resistance on the piston by its 
expansion, just at such a distance from the end of the stroke 
as the piston may be able to move through by its inertia. It 
is evident the adjustment of this will require great care and 
nicety of management. 

(79.) In 1797 a patent was granted totheliev. Mr. Cart- 
wright, a gentleman well known for other mechanical in- 
ventions, for some improvements in the steam-engine. His 
contrivance is at once so elegant and simple, that, although 
it has not been carried into practice, we cannot here pass it 
over without notice. 

The steam-pipe from the boiler is represented cut off at b 
(fig. 46.); T is a spindle-valve for admitting steam above the 
piston, and r is a spindle-valve in the piston ; d is a curved 
pipe forming a communication between the cylinder and the 
condenser, which is of very peculiar construction. Cart- 
wright proposed effecting a condensation without a jet, by ex- 
posing the steam to contact with a very large quantity of cold 
surface. For this purpose, he formed his condenser by placing 
two cylinders nearly equal in size one within the other, 
allowing the water of the cold cistern in which they were 
placed to flow through the inner cylinder, and to surround 
the outer one. Thus the thin space between the two cylin- 
ders formed the condenser. 

The air-pump is placed immediately under the cylinder, 
and the continuation of the piston-rod works its piston, which 
is solid and without a valve : f is the pipe from the conden- 
'ser to the air-pump, through which the condensed steam is 
drawn off through the valve a on the ascent of the piston, 
and on the descent, this is forced through a tube into a hot 
well, h, for the purpose of feeding the boiler through the 
feed pipe i. In the top of the hot well h is a valve which 
opens inwards, and is kept closed by a ball floating on the 
surface of the liquid. The pressure of the condensed air 



PI. IX 



Fy. ■// 




Pl.X. 



JTt'g. -J-6\ 




£rwi: tyJP.JKUvfriek. 



DOUBLE-CYLINDER ENGINES. 143 

above the surface of the liquid in h forces it through i into 
the boiler. When the air accumulates in too great a degree 
in h, the surface of the liquid is pressed so low that the ball 
falls and opens the valve, and allows it to escape. The air 
in h is that which is pumped from the condenser with the 
liquid, and which was disengaged from it. 

Let us suppose the piston at the top of the cylinder ; 
it strikes the tail of the valve t, and raises it, while the stem 
of the piston-valve r strikes the top of the cylinder, and is 
pressed into its seat. A free communication is at the same 
time open between the cylinder, below the piston and the 
condenser, through the tube d. The pressure of the steam 
thus admitted above the piston, acting against the vacuum 
below it, will cause its descent. On arriving at the bottom 
of the cylinder, the tail of the piston-valve r will strike the 
bottom, and it will be lifted from its seat, so that a commu- 
nication will be opened through it with the condenser. At 
the same moment a projecting spring, k, attached to the pis- 
ton-rod, strikes the stem of the steam-valve t, and presses it 
into its seat. Thus, while the further admission of steam is 
cut off, the steam above the piston flows into the condenser, 
and the piston being relieved from all pressure, is drawn up 
by the momentum of the fly-wheel, which continues the mo- 
tion it received from the descending force. On the arrival 
of the piston again at the top of the cylinder, the valve t is 
opened and r closed, and the piston descends as before, and 
so the process is continued. 

The mechanism by which motion is communicated from 
the piston to the fly-wheel is peculiarly elegant. On the 
axis of the fly-wheel is a small wheel with teeth, which work 
in the teeth of another large wheel l. This wheel is turned 
by a crank, which is worked by a cross-piece attached to the 
end of the piston-rod. Another equal-toothed wheel, m, is 
turned by a crank, which is worked by the other end of the 
cross-arm attached to the piston-rod. 

One of the peculiarities of this engine is, that the liquid 



144 THE STEAM ENGINE. 

which is used for the production of steam in the boiler cir- 
culates through the machine without either diminution or 
admixture with any other fluid, so that the boiler never 
wants more feeding than what can be supplied from the hot- 
well h. This circumstance forms a most important feature 
in the machine, as it allows of ardent spirits being used in 
the boiler instead of water, which, since they boil at low 
heats, promised a saving of half the fuel. The inventor even 
proposed, that the engine should be used as a still, as well 
as a mechanical power, in which case the whole of the fuel 
would be saved. 

In this engine, the ordinary method of rendering the pis- 
ton steam-tight, by oil or melted wax or tallow poured upon 
it, could not be applied, since the steam above the piston 
must always have a free passage through the piston-valve k. 
The ingenious inventor therefore contrived a method of mak- 
ing the piston steam-tight in the cylinder, without oil or 
stuffing, and his method has since been adopted with success 
in other engines. 

A ring of metal is graund into the cylinder, so as to fit it 
perfectly, and is then cut into four equal segments. The 
inner surface of this ring being slightly conical, another 
ring is ground into it, so as to fit it perfectly, and this is 
also cut into four segments, and one is placed within the 
other, but in such a manner that the joints or divisions do 
not coincide. The arrangement of the two rings is repre- 
sented in fig. 47. Within the inner ring are placed four 
springs, which press the pieces outward against the sides of 
the cylinder, and are represented in the diagram. Four 
pairs of these rings are placed one over another, so that their 
joints do not coincide, and the whole is screwed together by 
plates placed at top and bottom. A vertical section of the 
piston is given in fig. 48. 

One of the advantages of this piston is, that the longer it 
is worked, the more accurately it fits the cylinder, so that, 
as the machine wears it improves. 



LOCOMOTIVE ENGINES ON RAILWAYS. 145 

Metallic pistons have lately come into very general use, 
and such contrivances differ very little from the above. 



CHAPTER X. 



LOCOMOTIVE ENGINES ON RAILWAYS. 

High-pressure Engines. — Leupold's Engine. — Trevithick and Vivian. — 
Effects of Improvement in Locomotion. — Historical Account of the 
Locomotive Engine. — Blenkirisop's Patent. — Chapman's Improve- 
ment. — Walking Engine. — Stephenson's First Engines. — His Improve- 
ments. — Liverpool and Manchester Railway Company. — Their Pre- 
liminary Proceedings. — The Great Competition of 1829. — The Rocket. 
— The Sanspareil. — The Novelty. — Qualities of the Rocket. — Succes- 
sive Improvements. — Experiments. — Defects of the Present Engines. 
— Inclined Planes. — Methods of surmounting them. — Circumstances of 
the Manchester Railway Company. — Probable Improvements in Loco- 
motives. — Their capabilities with respect to speed. — Probable Effects 
of the Projected Rail-roads. — Steam Power compared with Horse 
Power. — Rail-roads compared with Canals. 

(80.) In the various modifications of the steam engine 
which we have hitherto considered, the pressure introduced 
on one side of the piston derives its efficacy either wholly or 
partially from the vacuum produced by condensation on the 
other side. This always requires a condensing apparatus, 
and a constant and abundant supply of cold water. An en- 
gine of this kind must therefore necessarily have considera- 
ble dimensions and weight, and is inapplicable to uses in 
which a small and light machine only is admissible. If the 
condensing apparatus be dispensed with, the piston will 
always be resisted by a force equal to the atmospheric pres- 
sure, and the only part of the steam pressure which will be 
available as a moving power, is that part by which it ex- 

19 



146 THE STEAM ENGINE. 

ceeds the pressure of the atmosphere. Hence, in engines 
which do not work by condensation, steam of a much higher 
pressure than that of the atmosphere is indispensably neces- 
sary, and such engines are therefore called high-pressure 
engines. 

We are not, however, to understand that every engine, in 
which steam is used of a pressure exceeding .that of the at- 
mosphere, is what is meant by a high-pressure engine; for 
in the ordinary engines in common use, constructed on 
Watt's principle, the safety-valve is loaded with from 3 to 
5 lbs. on the square inch ; and in Woolf's engines, the steam 
is produced under a pressure of 40 lbs. on the square inch. 
These would therefore be more properly called condensing 
engines than high-pressure engines; a term quite inappli- 
cable to those of Woolf. In fact, by high-pressure engines 
is meant engines in which no vacuum is produced, and, 
therefore, in which the piston works against a pressure equal 
to lhat of the atmosphere. 

In these engines, the whole of the condensing apparatus, 
viz. the cold-water cistern, condenser, air-pump, cold-water 
pump, &c. are dispensed with, and nothing is retained ex- 
cept the boiler, cylinder, piston, and valves. Consequently, 
such an engine is small, light, and cheap. It is portable also, 
and may be moved, if necessary, along with its load, and is 
therefore well adapted to locomotive purposes. 

(81.) High-pressure engines were one of the earliest mo- 
difications of the steam engine. The contrivance, which is 
obscurely described in the article already quoted (27.), from 
the Century of Inventions, is a high-pressure engine; for the 
power there alluded to is the elastic force of steam working 
against the atmospheric pressure. Newconien, in 1705, ap- 
plied the working-beam, cylinder, and piston to the atmo- 
spheric engine; and Leupold, about 1720, combined the 
working-beam and cylinder with the high-pressure prin- 
ciple, and produced the earliest high-pressure engine worked 



LOCOMOTIVE ENGINES ON RAILWAYS. 147 

by a cylinder and piston. The following is a description of 
LeiqioWs engine:- — 

a (fig. 49.) is the boiler, with the furnace beneath it; c c' 
are two cylinders with two solid pistons, p r', connected 
with the working-beams b b', to which are attached the 
pump-rods, r r', of two forcing-pumps, r r', which com- 
municate with a great force-pipe s ; a is a four-way cock 
(66.) already described. In the position in which it stands 
in the figure, the steam is issuing from below the piston p 
into the atmosphere, and the piston is descending by its own 
weight; steam from the boiler is at the same time pressing 
up the piston p', with a force equal to the difference between 
the pressure of the steam and that of the atmosphere. Thus 
the piston r of the forcing-pump is being drawn up, and the 
piston p' is forcing the piston r' down, and thereby driving 
water into the force-pipe s. On the arrival of the piston p 
at the bottom of the cylinder c, and p' at the top of the cy- 
linder c', the position of the cock is changed as represented 
in fig. 50. The steam, which has just pressed up the piston 
p', is allowed to escape into the atmosphere, while the steam, 
passing from the boiler below the piston p, presses it up, 
and thus p ascends by the steam pressure, and p' descends 
by its own weight. By these means the piston r is forced 
down, driving before it the water in the pump cylinder into 
the force-pipe s, and the piston r' is drawn up to allow the 
other pump-cylinder to be re-filled; and so the process is 
continued. 

A valve is placed in the bottom of the force-pipes, to pre- 
vent the water which has been driven into it from returning. 
This valve opens upwards ; and, consequently, the weight 
of the water pressing upon it only keeps it more effectually 
closed. On each descent of the piston, the pressure trans- 
mitted to the valve acting upwards being greater than the 
weight of the water resting upon it, forces it open, and an 
increased quantity of water is introduced. 

(82.) From the date of the improvement of Watt until 



148 THE STEAM ENGINE. 

the commencement of the present century, high-pressure 
engines were altogether neglected in these countries. In the 
year 1802, Messrs. Trevithick and Vivian constructed the 
first high-pressure engine which was ever brought into ex- 
tensive practical use in this kingdom. A section of this 
machine, made by a vertical plane, is represented in fig. 51. 

The boiler a b is a cylinder with flat circular ends. The 
fire-place is constructed in the following manner: — A tube 
enters the cylindrical boiler at one end; and, proceeding 
onwards, near the other extremity, is turned and recurved, 
so as to be carried back parallel to the direction in which it 
entered. It is thus conducted out of the boiler, at another 
part of the same end at which it entered. One of the ends 
of this tube communicates with the chimney e, which is 
carried upwards, as represented in the figure. The other 
mouth is furnished with a door; and in it is placed the grate, 
which is formed of horizontal bars, dividing the tube into 
two parts; the upper part forming the fire-place, and the 
lower the ash-pit. The fuel is maintained in a state of com- 
bustion, on the bars, in that part of the tube represented at 
c d; and the flame is carried by the draft of the chimney 
round the curved flue, and issues at e into the chimney. 
The flame is thus conducted through the water, so as to ex- 
pose the latter to as much heat as possible. 

A section of the' cylinder is represented at f, immersed in 
the boiler, except a few inches of the upper end, where the 
four-way cock g is placed for regulating the admission of the 
steam. A tube is represented at h, which leads from this 
four-way cock into the chimney ; so that the waste steam, 
after working the piston, is carried off through this tube, 
and passes into the chimney. The upper end of the piston- 
rod is furnished with a cross-bar, which is placed in a direc- 
tion at right angles to the length of the boiler, and also to 
the piston-rod. This bar is guided in its motion by sliding 
on two iron perpendicular rods fixed to the sides of the 
boiler, and parallel to each other. To the ends of this cross- 



LOCOMOTIVE ENGINES ON RAILWAYS. 149 

bar are joined two connecting-rods, the lower ends of which 
work two cranks fixed on an axis extending across and he- 
neath the boiler, and immediately under the centre of the 
cylinder. This axis is sustained in bearings formed in the 
legs which support the boiler, and upon its extremity is 
fixed the fly-wheel as represented at b. . A large-toothed 
wheel is placed on this axis; which, being turned with the 
cranked axle, communicates motion to other wheels ; and, 
through them, to any machinery which the engine may be 
applied to move; 

As the four-way cock is represented in the figure, the 
steam passes from the boiler through the curved passage g 
above the piston, while the steam below the piston is carried 
off through a tube which does not appear in the figure, by 
which it is conducted to the tube h, and thence to the chim- 
ney. The steam, therefore, which passes above the piston 
presses it downwards; while the pressure upwards does not 
exceed that of the atmosphere. The piston will therefore 
descend with a force depending on'the excess of the pressure 
of. the steam produced in the boiler above the atmospheric 
pressure. When the piston has arrived at the bottom of 
the cylinder, the cock is made to assume the position re- 
presented in the figure 52. This effect is produced by the 
motion of the piston-rod. The steam now passes from 
above the piston, through the tube h, into the chimney, 
while the steam from the boiler is conducted through another 
tube below the piston. The pressure above the piston, in 
this case, does not exceed that of the atmosphere ; while the 
pressure below it will be that of the steam in the boiler. 
The piston will therefore ascend with the difference of these 
pressures. On the arrival of the piston at the top of the 
cylinder, the four-way cock is again turned to the position 
represented in fig. 51., and the piston again descends ; and 
in the same manner the process is continued. A safety- 
valve is placed on the boiler at v, loaded with a weight w, 



150 



THE STEAM ENGINE. 



proportionate to the strength of the steam with which it is 
proposed to work. 

In the engines now described, this valve was frequently 
loaded at the rate of from 60 to 80 lbs. on the square inch. 
As the boilers of high-pressure engines were considered 
more liable to accidents from bursting than thbsein which 
steam of a lower pressure was used, greater precautions 
were taken against such effects. A second safety-valve was 
provided, which was not left in the power of the engine- 
man. By this means he had a power to diminish the pres- 
sure of the steam, but could not increase it beyond the limit 
determined by the valve which was removed from his inter- 
ference. The greatest cause of danger, however, arose from 
the water in the boiler being consumed by evaporation faster 
than it was supplied; and therefore falling below the level 
of the tube containing the furnace. To guard against acci- 
dents arising from this circumstance, a hole was bored in the 
boiler, at a certain depth, below which the water should not 
be allowed to fall; and in this hole a plug of metal was 
soldered with lead, or with some other metal, which would 
fuse at that temperature which would expose the boiler to 
danger. Thus, in the event of the water being exhausted, 
so that its level would fall below the plug, the heat of the 
furnace would immediately melt the solder, and the plug 
would fall out, affording a vent for the steam, without 
allowing the boiler to burst. The mercurial steam-gauge, 
already described, was also used as an additional security. 
When the force of the steam exceeded the length of the 
column of mercury which the tube would contain, the mer- 
cury would be blown out, and the tube would give vent to 
the steam. The water by which the boiler was replenished 
was forced into it by a pump worked by the engine. In 
order to economise the heat, this water was contained in a 
tube t, which surrounded the pipe h. As the waste steam, 
after working the piston, passed off through h, it imparted a 
portion of its heat to the water contained in the tube t, 



PI. X! 



Fig. /n. 





~FtyS0 




Hn„r. /-rj' V, rrit'i'/l 



LOCOMOTIVE ENGINES ON RAILWAYS. 151 

which was thus warmed to a certain temperature before it 
was forced into the boiler by the pump. Thus a part of the 
heat, which was originally carried from the boiler in the form 
of steam, was returned again to the boiler with the water 
with which it was fed. 

It is evident that engines constructed in this manner may 
be applied to all the purposes to which the condensing en- 
gines are applicable. 

(e) To the plates of the English edition has need added 
one, (plate A) representing a high-pressure engine as con- 
structed by the West Point Foundry in the state of New 
York. The principal parts will be readily distinguished 
from their resemblance to the analogous parts of a con- 
densing engine. The condenser and air pump of that en- 
gine, it will be observed, are suppressed. Atva; and y z 
are forcing pumps by which a supply of water is injected 
into the boiler at each motion of the engine. For the four- 
way cock, used in the English high-pressure engines, a slide 
valve at r s, is substituted, and is found to work to much 
greater advantage. It is set in motion by an eccentric, in a 
manner that will be more obvious from an inspection of the 
plate than from any description. — A. e. 

(/*) A very safe and convenient boiler for a high pressure 
engine has been invented in the United States by Mr. Bab- 
cock. The boiler consists of small tubes, into which water 
is flashed by a small forcing pump at every stroke of the 
engine. The tubes are kept so hot in a furnace, as to gene- 
rate steam of the required temperature, but not hot enough 
to cause any risk of the decomposition of the water. The 
strength of the apparatus is such, and the quantity of water 
exposed to heat at one time so small, as to leave hardly any 
risk of danger. — A. e. 

(83.) Two years after the date of the patent of this engine, 
its inventor constructed a machine of the same kind for the 
purpose of moving carriages on railroads; and applied it 
successfully, in the year 1804, on the railroad at Merthyr 



1 52 THE STEAM ENGINE. 

Tydvil, in South Wales. It was in principle the same as 
that already described. The cylinder however was in a 
horizontal position, the piston-rod working in the direction 
of the line. of road: the extremity of the piston-rod, by 
means of a connecting-rod, worked cranks placed on the 
axletree, on which were fixed two cogged wheels: these 
worked in others, by which their motion was communicated 
finally to cogged wheels fixed on the axle of the hind wheels 
of the carriage, by which this axle was kept in a state of re- 
volution. The hind wheels being fixed on the axletree, and 
turning with it, were caused likewise to revolve ; and so 
long as the weight of the carriage did not exceed that which 
the friction of the road was capable of propelling, the car- 
riage would thus be moved forwards. On this axle was 
placed a fly-wheel to continue the rotatory motion at the 
termination of each stroke. The fore wheels are described 
as being capable of turning like the fore wheels of a carriage, 
so as to guide the vehicle. The projectors appear to have 
contemplated, in the first instance, the use of this carriage 
on turnpike roads; but that notion seems to have been aban- 
doned, and its use was only adopted on the railroad before 
mentioned. On the occasion of its first trial, it drew after 
it as many carriages as contained 10 tons of iron a distance 
of nine miles; which stage it performed without any fresh 
supply of water, and travelled at the rate of five miles an 
hour. 

(84.) Capital and skill have of late years been directed 
with extraordinary energy to the improvement of inland 
transport; and thisimportant instrument of national wealth 
and civilisation has received a proportionate impulse. Ef- 
fects are now witnessed, which, had they been narrated a 
few years since, could only have been admitted into the 
pages of fiction or volumes of romance. Who could have" 
credited the possibility of a ponderous engine .of iron, load- 
ed with several hundred passengers, in a train of carriages 
of corresponding magnitude, and a large quantity of water 



LOCOMOTIVE ENGINES ON RAILWAYS. 153 

and coal, taking flight from Manchester and arriving at Li- 
verpool, a distance of about thirty miles, in little more than 
an hour? And yet this is a matter of daily and almost hour- 
ly occurrence. Neither is the road, on which this wondrous 
performance is effected, the most favourable which could be 
constructed for such machines. It is subject to undulations 
and acclivities, which reduce the rate of speed much more 
than similar inequalities affect the velocity on common roads. 
The rapidity of transport thus attained is not less wonderful 
than the weights transported. Its capabilities in this re- 
spect far transcend the exigencies even of the two greatest 
commercial marts in Great Britain. Loads, varying from 
50 to 150 tons are transported at the average rate of 15 miles 
an hour ; but the engines in this case are loaded below their 
power ; and in one instance we have seen a load — we should 
rather say a cargo — of wagons, conveying merchandise to 
the amount of 230 tons gross, transported from Liverpool to 
Manchester at the average rate of 12 miles an hour. 

The astonishment with which such performances must be 
viewed, might be qualified, if the art of transport by steam 
on railways had been matured, and had attained that full 
state of perfection which such an art is always capable of re- 
ceiving from long experience, aided by great scientific know- 
ledge, and the unbounded application of capital. But such is 
not the present case. The art of constructing locomotive 
engines, so far from having attained a state of maturity, has 
not even emerged from its infancy. So complete was the 
ignorance of its powers which prevailed, even among engi- 
neers, previous to the opening of the Liverpool railway, that 
the transport of heavy goods was regarded as the chief ob- 
ject of the undertaking, and its principal source of revenue. 
The incredible speed of transport, effected even in the very 
first experiments in 1830, burst upon the public, and on the 
scientific world, with all the effect of a new and unlooked- 
for phenomenon. On the unfortunate occasion which de- 
prived this country of Mi\ Huskisson, the wounded body of 

20 



154 THE STEAM ENGINE. 

that statesman was transported a distance of about fifteen 
miles in twenty -fire minutes, being at the rate of thirty-six 
miles an hour. The revenue of the road arising from pas- 
sengers since its opening, has, contrary to all that was fore- 
seen, been nearly double that which has been derived from 
merchandise. So great was the want of experience in the 
construction of engines, that the company was at first igno- 
rant whether they should adopt large steam-engines fixed at 
different stations on the line, to pull the carriages from sta- 
tion to station, or travelling engines to drag the loads the 
entire distance. Having decided on the latter, they have, 
even to the present moment, laboured under the disadvan- 
tage of the want of that knowledge which experience alone 
can give. The engines have been constantly varied in their 
weight and proportions, in their magnitude and form, as the 
experience of each successive month has indicated. As de- 
fects became manifest they were remedied ; improvements 
suggested were adopted ; and each quarter produced engines 
of such increased power and efficiency, that their predeces- 
sors were abandoned, not because they were worn out, but 
because they, had been outstripped in the rapid march of im- 
provement. Add to this, that only one species of travelling 
engine has been effectively tried ; the capabilities of others 
remain still to be developed ; and even that form of engine 
which has received the advantage of a course of experiments 
on so grand a scale to carry it towards perfection, is far short of 
this point, and still has defects, many of which, it is obvious, 
time and experience will remove. If then travelling steam 
engines, with all the imperfections of an incipient invention 
— with the want of experience, the great parent of practical 
improvements — with the want of the common advantage of 
the full application of the skill and capital of the country — 
subjected to but one great experiment, and that experiment 
limited to one form of engine ; if, under such disadvantages, 
the effects to which we have referred have been produced, 
what may we not expect from this extraordinary power, 



LOCOMOTIVE ENGINES ON RAILWAYS. 155 

when (he enterprise of the country shall be unfettered, when 
greater fields of experience are opened, when time, inge- 
nuity, and capital have removed the existing imperfections, 
and have brought to light new and more powerful princi- 
ples ? This is not mere speculation on possibilities, but re- 
fers to what is in a state of actual progression. Railways are 
in progress between the points of greatest intercourse in the 
United Kingdom, and travelling steam engines are in prepa- 
ration for the common turnpike roads; the practicability and 
utility of that application of the steam engine having not on- 
ly been established by experiment to the satisfaction of their 
projectors, but proved before the legislature in a committee 
of inquiry on the subject. 

The important commercial and political effects attending 
such increased facility and speed in the transport of persons 
and goods, are too obvious to require any very extended no- 
tice here. • A part of the price (and in many cases a consi- 
derable part) of every article of necessity or luxury, consists 
of the cost of transporting it from the producer to the con- 
sumer; and consequently every abatement or saving in this 
cost must produce a corresponding reduction in the price of 
every article transported; that is to say, of everything which 
is necessary for the subsistence of the poor, or for the enjoy- 
ment of the rich, of every comfort, and of every luxury of 
life. The benefit of this will extend, not to the consumer 
only, but to the producer: by lowering the expense of tran- 
sport of the produce, whether of the soil or of the loom, a 
less quantity of that produce will be spent in bringing the 
remainder to market, and consequently a greater surplus will 
reward the labour of the producer. The benefit of this will 
be felt even more by the agriculturist than by the manufac- 
turer; because the proportional cost of transport of the pro- 
duce of the soil is greater than that of manufactures. If 200 
quarters of corn be necessary to raise 400, and 100 more be 
required to bring the 400 to market, then the net surplus will 
be 100. But if by the use of steam carriages the same quan- 



156 THE STEAM ENGINE. 

tity can be brought to market with an expenditure of 50 
quarters, then the net surplus will be increased from 100 to 
150 quarters; and either the profit of the farmer, or the rent 
of the landlord, must be increased by the same amount. 

But the agriculturist would not merely be benefited by 
an increased return from the soil already under cultivation. 
Any reduction in the cost of transporting the produce to 
market would call into cultivation tracts of inferior fertility, 
the returns from which would not at present repay the cost 
of cultivation and transport. Thus land would become pro- 
ductive which is now waste, and an effect would be produced 
equivalent to adding so much fertile soil to the present ex- 
tent of the country. It is well known, that land of a given 
degree of fertility will yield increased produce by the in- 
creased application of capital and labour. By a reduction in 
the cost of transport, a saving will be made which may ena- 
ble the agriculturist to apply to tracts already under cultiva- 
tion the capital thus saved, and thereby increase {heir actual 
production. Not only, therefore, would such an effect be 
attended with an increased extent of cultivated land, but also 
with an increased degree of cultivation in that which is 
already productive. 

It has been said, that in Great Britain there are above a 
million of horses engaged in various ways in the transport 
of passengers and goods, and that to support each horse re- 
quires as much land as would, upon an average, support 
eight men. If this quantity of animal power were displaced 
by steam engines, and the means of transport drawn from 
.the bowels of the earth, instead of being raised upon its sur- 
face, then, supposing the above calculation correct, as much 
land would become available for the support of human beings 
as would suffice for an additional population of eight millions; 
or, what amounts to the same, would increase the means of 
support of the present population by about one-third of the 
present available means. The land which now supports 



LOCOMOTIVE ENGINES ON RAILWAYS. 157 

horses for transport would then support men, or produce 
corn for food. 

The objection that a quantity of land exists in the country 
capable of supporting horses alone, and that such land would 
be thrown out of cultivation, scarcely deserves notice here. 
The existence of any considerable quantity of such land is 
extremely doubtful. What is the soil which will feed a 
horse and not feed oxen or sheep, or produce food for man? 
But even if it be admitted that there exists in the country a 
small portion of such land, that portion cannot exceed, nor 
indeed equal, what would be sufficient for the number of 
horses which must after' all continue to be employed for the 
purposes of pleasure, and in a variety of cases where steam 
must necessarily be inapplicable. It is to be remembered, 
also, that the displacing of horses in one extensive occupa- 
tion, by diminishing their price must necessarily increase 
the demand for them in others. 

The reduction in the cost of transport of manufactured 
articles, by lowering their price in the market, will stimu- 
late their consumption. This observation applies of course 
not only to home but to foreign markets. In the latter we 
already in many branches of manufacture command a mono- 
poly. The reduced price which we shall attain by cheap- 
ness and facility of transport will still further extend and 
increase our. advantages. The necessary consequence will 
be, an increased demand for manufacturing population; and 
this increased population again reacting on the agricultural 
interests, will form an increased market for that species of 
produce. So interwoven and complicated are the fibres 
which form the texture of the highly civilized and artificial 
community in which we live, that an effect produced on any 
one point is instantly transmitted to the most remote and 
apparently unconnected parts of the system. 

The two advantages of increased cheapness and speed, 
besides extending the amount of existing traffic, call into ex- 
istence new objects of commercial intercourse. For the 



158 THE STEAM ENGINE. 

same reason that the reduced cost of transport, as we have 
shown, calls new soils into cultivation, it also calls into ex- 
istence new markets for manufactured and agricultural pro- 
duce. The great speed of transit which has been proved to 
be practicable, must open a commerce between distant points 
in various articles, the nature of which does not permit them 
to be preserved so as to be fit for use bevond a certain time. 
Such are, for example, many species of vegetable and ani- 
mal food, which at present are confined to markets at a very 
limited distance from the grower or feeder. The truth of 
this observation is manifested by the effects which have fol- 
lowed the intercourse by steam on the Irish Channel. The 
western towns of England have become markets for a pro- 
digious quantity of Irish produce, which it had been previ- 
ously impossible to export. If animal food be transported 
alive from the grower to the consumer, the distance of the 
market is limited by the power of the animal to travel, and 
the cost of its support on the road. It is only particular spe- 
cies of cattle which bear to be carried to market on common 
roads and by horse carriages. But the peculiar nature of a 
railway, the magnitude and weight of the loads which may 
be transported on it, and the prodigious speed which may 
be attained, render the transport of cattle, of every species, 
to almost any distance, both easy and cheap. In process of 
time, when the railway system becomes extended, the me- 
tropolis and populous towns will therefore become markets, 
not as at present to districts within limited distances of them, 
but to the whole country. 

The moral and political consequences of so great a change 
in the powers of transition of persons and intelligence from 
place to place are not easily calculated. The concentration 
of mind and exertion which a great metropolis always ex- 
hibits, will be extended in a considerable degree to the whole 
realm. The same effect will be produced as if all distances 
were lessened in the proportion in which the speed and 
cheapness of transit are increased. Towns, at present re- 



LOCOMOTIVE ENGINES ON RAILWAYS. 159 

moved some stages from the metropolis, will become its 
suburbs; others, now a day's journey, will be removed to its 
immediate vicinity ; business will be carried on with as much 
ease between them and the metropolis, as it is now between 
distant points of the metropolis itself. Let those who discard 
speculations like these as wild and improbable, recur to the 
state of public opinion, at no very remote period, on the sub- 
ject of steam navigation. Within the memory of persons 
who have not yet passed the meridian of life, the possibility 
of traversing by the steam engine the channels and seas that 
surround and intersect these islands, was regarded as the 
dream of enthusiasts. Nautical men and men of science re- 
jected such speculations with equal incredulity, and with 
little less than scorn for the understanding of those who 
could for a moment entertain them. Yet we have witnessed 
steam engines traversing not these channels and seas alone, 
but sweeping the face of the waters round every coast in Eu- 
rope. The seas which interpose between our Asiatic do- 
minions and Egypt, and those which separate our own 
shores from our West Indian possessions, have offered an 
equally ineffectual barrier to its powers. Nor have the ter- 
rors of the Pacific prevented the "Enterprise" from doubling 
the Cape, and reaching the shores of India. If steam be not 
used as the only means of connecting the most distant points 
of our planet, it is not because it is inadequate to the accom- 
plishment of that end, but because the supply of the material 
from which at the present moment it derives its powers, is 
restricted by local and acccidental circumstances.* 

We propose in the present chapter to lay before our rea- 
ders some account of the means whereby the effects above 
referred to have been produced; of the manner and degree 
in which the public have availed themselves of these means; 

* Some of the preceding observations on inland transport, as well as 
other parts of the present chapter, appeared in articles written by me in 
the Edinburgh Review for October, 1832, and October, 1834. 



160 THE STEAM ENGINE. 

and of the improvements of which they seem to us to be 
susceptible. 

(85.) It is a singular fact, that in the history of this inven- 
tion considerable time and great ingenuity were vainly ex- 
pended in attempting to overcome a difficulty, which in the 
end turned out to be purely imaginary. To comprehend 
distinctly the manner in which a wheel carriage is propelled 
by steam, suppose that a pin or handle is attached to the 
spoke of the wheel at some distance from its centre, and that 
a force is applied to this pin in, such a manner as to make 
the wheel revolve. If the face of the wheel and the surface 
of the road were absolutely smooth and- free from friction, 
so that the face of the wheel would slide without resistance 
upon the road, then the effect of the force thus applied would 
be merely to cause the wheel to turn round, the carriage be- 
ing stationary, the surface of the wheel would slip or slide 
upon the road as the wheel is made to revolve. But if, on 
the other hand, the pressure of the face of the wheel upon 
the road is such as. to produce between them such a degree 
of adhesion as will render it impossible for the wheel to 
slide or slip upon the road by the force which is applied to 
it, the consequence will be, that the wheel can only turn 
round in obedience to the force which moves it by causing 
the carriage to advance, so that the wheel will roll upon the 
road, and the carriage will be moved forward, through a dis- 
tance equal to the circumference of the wheel, each time it 
performs a complete revolution. 

It is obvious that both of these effects may be partially 
produced; the adhesion of the wheel to the road may be in- 
sufficient to prevent slipping altogether, and yet it may be 
sufficient to prevent the wheel from slipping as fast as it re- 
volves. Under such circumstances the carriage would ad- 
vance and the wheel would slip. The progressive motion 
of the carriage during one complete revolution of the wheel 
would be equal to the difference between the complete cir- 



LOCOMOTIVE ENGINES ON RAILWAYS. 161 

cumference of the wheel and the portion through which in 
one revolution it has slipped. 

When the construction of travelling steam engines first 
engaged the attention of engineers, and for a considerable 
period afterwards, a notion was impressed upon their minds 
that the adhesion between the face of the wheel and the sur- 
face of the road must necessarily be of very small amount, 
and that in every practical case the wheels thus driven would 
either slip altogether, and produce no advance of the car- 
riage, or that a considerable portion of the impelling power 
would be lost by the partial slipping or sliding of the wheels. 
It is singular that it should never have occurred to the many 
ingenious persons who for several years were engaged in 
such experiments and speculations, to ascertain by experi- 
ment the actual amount of adhesion in any particular case 
between the wheels and the road. Had they done so, we 
should probably now have found locomotive engines in a 
more advanced state than that to which they have attained. 

To remedy this imaginary difficulty, Messrs. Trevithick 
and Vivian proposed to make the external rims of the 
wheels rough and uneven, by surrounding them with pro- 
jecting heads of nails or bolts, or by cutting transverse 
grooves on them. They proposed, in cases where consider- 
able elevations were to be ascended, to cause claws or nails 
to project from the surface during the ascent, so as to take 
hold of the road. 

In seven years after the construction of the first locomo- 
tive engine by these engineers, another locomotive engine 
was constructed by Mr. JBlinkensop, of Middleton Colliery, 
near Leeds. He obtained a patent, in 1811, for the appli- 
cation of a rack-rail. The rail-road thus, instead of being 
composed of smooth bars of iron, presented a line of project- 
ing teeth, like those of a cog-wheel, which stretched along 
the entire distance to be travelled. The wheels on which 
the engine rolled were furnished with corresponding teeth, 

21 



162 



THE STEAM ENGINE. 



which worked in the- teeth of the railroad; and, in this way, 
produced a progressive motion in the carriage. 

The next contrivance for overcoming this fictitious diffi- 
culty, was that of Messrs. Chapman^ who, in the year 1812, 
obtained a patent for working a locomotive engine by a 
chain extending along the middle of the line of railroad, from 
the one end to the other. This chain was passed once round 
a grooved wheel under the centre of the carriage ; so that, 
when, this grooved wheel was turned by the engine, the 
chain being incapable of slipping upon it, the carriage was 
consequently advanced on the road. In order to prevent 
the strain from acting on the whole length of the chain, its 
links were made to fall upon upright forks placed at certain 
intervals, which between those intervals sustained the ten- 
sion of the chain produced by the engine. Friction-rollers 
were used to press the chain into the groove of the wheel, 
so as to prevent it from slipping. This contrivance was soon 
abandoned, for the very obvious reason that a prodigious 
loss of force was incurred by the friction of the chain. 

The following year, 1813, produced a contrivance, of sin- 
gular ingenuity, for overcoming the supposed difficulty aris- 
ing from the want of adhesion between the wheels and the 
road. This was no other than a pair of mechanical legs and 
feet, which were made to walk and propel in a manner some- 
what resembling the feet of an animal. 

A sketch of these propellers is given in fig. 53. a is the 




LOCOMOTIVE ENGINES ON RAILWAYS. 163 

carriage moving on the railroad, l and l' are the legs, f and 
f' the feet. The foot f has a joint at o, which corresponds to 
the ankle; another joint is placed at k, which corresponds to 
the knee; and a third is placed at l, which corresponds to the 
hip. Similar joints are placed at the corresponding letters in 
the other leg. The knee-joint k is attached to the end of the 
piston of the cylinder. When the piston, which is horizon- 
tal's pressed outwards, the lego, presses the foot f against 
the ground, and the resistance forces the carriage A onwards. 
As the carriage proceeds, the angle k at the knee becomes 
larger, so that the leg and thigh take a straighter position ; 
and this continues until the piston has reached the end of its 
stroke. At the hip l there is a short lever, l m, the extre- 
mity of which is connected by a cord or chain with a point, 
s, placed near the shin of the leg. When the piston is pressed 
into the cylinder, the knee, k, is drawn towards the engine, 
and the cord, m, s, is made to lift the foot, f, from the ground ; 
to which it does not return until the piston has arrived at the 
extremity of the cylinder. On the piston being again driven, 
out of the cylinder, the foot, f, being placed on the road, 
is pressed backwards by the force of the piston-rod at z; 
but the friction of the ground preventing its backward mo- 
tion, the re-action causes the engine to advance : and in the 
same manner this process is continued. 

Attached to the thigh, at n, above the knee, by a joint, is 
a horizontal rod, n r, which works a rack, r. This rack has 
beneath it a cog-wheel. This cog-wheel acts in another rack 
below it. By these means, when the knee k is driven from 
the engine, the rack r is moved backwards; but the cog- 
wheel, acting on the other rack beneath it, will move the 
latter in the contrary direction. The rack r being then 
moved in the same direction ivith the knee, k, it follows 
that the other rack will always be moved in a contrary di- 
rection. The lower rack is connected by another horizon- 
tal rod with the thigh of the leg, l f', immediately above 
the knee, at n'. When the piston is forced inwards, the 
the knee, k', will thus be forced backwards ; and when the 



164 THE STEAM ENGINE. 

piston is forced outwards, the knee, k', will be drawn for- 
wards. It therefore follows that the two knees, k and k', 
are pressed alternately backwards and forwards. The 
foot, f', when the knee, k', is drawn forward, is lifted by the 
means already described for the foot, v. 

It will be apparent, from this description, that the piece 
of mechanism here exhibited is a contrivance derived from 
the motion of the legs of an animal, and resembling in all 
respects the fore legs of a horse. It is however to be re- 
garded rather as a specimen of great ingenuity than as a con- 
trivance of practical utility. 

(86.) It was about this period that the important fact 
was first ascertained that the adhesion or friction of the 
wheels with the rails on which they moved was amply suf- 
ficient to propel the engine, even when dragging after it a 
load of great weight ; and that in such case, the progressive 
motion would be effected without any slipping of the wheels. 
The consequence of this fact rendered totally useless all the 
contrivances for giving wheels a purchase on the road, such 
as racks, chains, feet, &c. The experiment by which this 
was determined appears to have been first tried on the Wy- 
lam railroad ; where it was proved, that, when the road 
was level, and the rails clean, the adhesion of the wheels was 
sufficient, in all kind of weather, to propel considerable loads. 
By manual labour it was first ascertained how much weight 
the "Wheels of a common carriage would overcome without 
slipping round on the rail ; and having found the proportion 
which that bore to the weight, they then ascertained that the 
weight of the engine would produce sufficient adhesion to 
drag after it, on the railroad, the requisite number of wa- 
gons.* 

In 1814, an engine was constructed at Killingworth, by 
Mr. Stephenson, having two cylinders with a cylindrical 
boiler, and working two pair of wheels, by cranks placed at 

* Wood on Railroads, 2d edit. 



LOCOMOTIVE ENGINES ON RAILWAYS. 



165 



right angles ; so that when the one was in full operation, the 
other was at its dead points. By these means the propelling 
power was always in action. The cranks were maintained 
in this position by an endless chain, which passed round two 
cogged wheels placed under the engine, and which were 
fixed on the same axles on which the wheels were placed. 
The wheels in this case were fixed on the axles, and turned 
with them. 

This engine is represented in fig. 54., the sides being open, 
to render the interior mechanism visible, a b is the cylin- 
drical boiler; c c are the working cylinders; d e are the 



P^3 




cogged wheels fixed on the axle of the wheels of the engine, 
and surrounded by the endless chain. These wheels being 
equal in magnitude, perform their revolutions in the same 
time; so that, when the crank, f, descends to the lowest 
point, the crank, g, rises from the lowest point to the hori- 
zontal position, d; and, again, when the crank, f, rises 
from the lowest point to the horizontal position, e, the other 
crank rises to the highest point ; and so on. A very beau- 
tiful contrivance was adopted in this engine, by which it was 
suspended on springs of steam. Small cylinders, represent- 
ed at h, are screwed by flanges to one side of the boiler, and 
project within it a few inches; they have free communica- 



166 THE STEAM ENGINE. 

tion at the top with the water or steam of the boiler. Solid 
pistons are represented at i, which move sleam-tight in these 
cylinders; the cylinders are open at the bottom, and the 
piston-rods are screwed on the carriage of the engine, over 
the axle of each pair of wheels, the pistons being presented 
upwards. As the engine is represented in the figure, it is 
supported on four pistons, two at each side. The pistons 
are pressed upon by the water or steam which occupies the 
upper chamber of the cylinder; and the latter being elastic 
in a high degree, the engine has all the advantage of spring 
suspension. The defect of this method of supporting the 
engine is, that when the steam loses that amount of elasticity 
necessary for the support of the machine, the pistons are 
forced into the cylinders, and the bottoms of the cylinders 
bear upon them. All spring suspension is then lost. This 
mode of suspension has consequently since been laid aside. 

In an engine subsequently constructed by Mr. Stephenson, 
for the Killingworth railroad, the mode adopted of connect- 
ing the wheels by an endless chain and cog-wheels was 
abandoned ; and the same effect was produced by con- 
necting the two cranks by a straight rod. All such con- 
trivances, however, have this great defect, that, if the fore 
and hind wheels be not constructed with dimensions accu- 
rately equal, there must necessarily be a slipping or dragging 
on the road. The nature of the machinery requires that 
each wheel should perform its revolution exactly in the same 
time; and consequently, in doing so, must pass over exaetly 
equal lengths of the road. If, therefore, the circumference 
of the wheels be not accurately equal, that wheel which has 
the lesser circumference must be dragged along so much of 
the road as that by which it falls short of -the circumference 
of the greater wheel ; or, on the other hand, the greater 
must be dragged in the opposite direction, to compensate for 
the same difference. As no mechanism can accomplish a 
perfect equality in four, much less in six, wheels, it may be 
assumed that a great portion of that dragging effect is a ne- 



LOCOMOTIVE ENGINES ON RAILWAYS. 167 

cessary consequence of the principle of this machine ; and 
even were the wheels, in the first instance, accurately con- 
structed, it is not possible that their wear could be so ex- 
actly uniform as to continue equal. 

(87.) The next stimulus which the progress of this inven- 
tion received, proceeded from the great national work under- 
taken at Liverpool, by which that town and the extensive 
commercial mart of Manchester were connected by a double 
line of railway. When this project was undertaken, it was 
not decided what moving power it might be most expedient 
to adopt as a means of transport on the proposed road: the 
choice lay between horse-power, fixed steam engines, and 
locomotive engines; but the first, for many obvious reasons, 
was at once rejected in favour of one or other of the last 
two. 

The steam engine may be applied, by two distinct 
methods, to move wagons either on a turnpike road or on 
a railway. By the one method the steam engine is fixed, 
and draws the carriage or train of carriages towards it by a 
chain extending the whole length of road on which the en- 
gine works. By this method the line of road over which 
the transport is conducted is divided into a number of short 
intervals, at the extremity of each of which an engine is 
placed. The wagons or carriages, when drawn by any en- 
gine to its own station, or detached, and connected with the 
extremity of the chain worked by the next stationary engine; 
and thus the journey is performed, from station to station, 
by separate engines. By the other method the same engine 
draws the load the whole journey, travelling with it. 

The Directors of the Liverpool and Manchester railroad, 
when that work was advanced towards its completion, em- 
ployed, in the spring of the year 1829, Messrs. Stephenson 
and Lock and Messrs. Walker and Rastrick, experienced 
engineers, to visit the different railways where practical in- 
formation respecting the comparative effects of stationary 
and locomotive engines was likely to be obtained; and from 



168 



THE STEAM ENGINE. 



these gentlemen they received reports on the relative merits, 
according to their judgment, of the two methods. The par- 
ticulars of their calculations are given at large in the valua- 
ble work of Mr. Nicholas Wood on railways; to which we 
refer the reader, not only on this, but on many other subjects 
connected with the locomotive steam engine into which it 
would be foreign to our subject to enter. The result of the 
comparison of the two systems was, that the capital neces- 
sary to be advanced to establish a line of stationary engines 
was considerably greater than that which was necessary to 
establish an equivalent power in locomotive engines; that 
the annual expense by the stationary engines was likewise 
greater; and that, consequently, the expense of transport by 
the latter was greater, in a like proportion. The subjoined 
table exhibits the results numerically: — 





Capital. 


Annual 
Expense. 


Expense of 
taking a Ton of 
Goods One Mile. 


Locomotive Engines 
Stationary Engines - - 

Locomotive System — less_ 


£ s. d. 

58,000 

121,496 7 


£ s. d. 
25,517 8 2 
42,031 16 5 


0-164 of a penny. 
0-269 


63,496 7 


16,514 8 3 


0-105 



On the score of economy, therefore, the system of loco- 
motive engines was entitled to a preference ; but there were 
other considerations which conspired with this to decide the 
choice of the Directors in its favour. An accident occurring 
in any part of a road worked by stationary engines must ne- 
cessarily produce a total suspension of work along the entire 
line. The most vigilant and active attention on the part of 
every workman, however employed, in every part of the 
line, would therefore be necessary ; but, independently of 
this, accidents arising from the fracture or derangement of 
any of the chains, or from the suspension of the working of 
any of the fixed engines, would be equally injurious, and 



LOCOMOTIVE ENGINES ON RAILWAYS. 1,69 

would effectually stop the intercourse along the line. On 
the other hand, in locomotive engines an accident could on- 
ly affect the particular train of carriages drawn by the engine 
to which the accident might occur; and even then the diffi- 
culty could be remedied by having a supply of spare engines 
at convenient stations along the line. It is true that 'the 
probability of accident is, perhaps, less in the stationary 
. than in the locomotive system ; but the injurious conse- 
quences, when accident does happen, are prodigiously greater 
in the former. "The one system," says Mr. Walker, "is 
like a chain extending from Liverpool to Manchester, the 
failure of a single link of which would destroy the whole ; 
while the other is like a number of short and unconnected 
chains," the destruction of any one of which does not inter- 
fere with the effect of the others, and the loss of which may 
be supplied with facility. 

The decision of the Directors was, therefore, in favour of 
locomotive engines ; and their next measure was to devise 
some means by which the inventive genius of the country 
might be stimulated to supply them with the best possible 
form of engines for this purpose. With this view, it was 
proposed and carried into effect to offer a prize for the best 
locomotive engine which might be produced under certain 
proposed conditions, and to appoint a time for a public trial 
of the claims of the candidates. A premium of 500/. was ac- 
cordingly offered for the best locomotive engine to run on 
the Liverpool and Manchester Railway ; under the condi- 
tion that it should produce no smoke ; that the pressure of 
the steam should be limited to 50 lbs. on the inch ; and that 
it should draw at least three times its own weight, at the 
rate of not less than ten miles an hour ; that the engine 
should be supported on springs, and should not exceed fif- 
teen feet in height. Precautions were also proposed against 
the consequences of the boiler bursting ; and other matters, 
not necessary to mention more particularly here. This pro- 
posal was announced in the spring of 1829, and the time of 

22 



170 THE STEAM ENGINE. 

trial was appointed in the following October. The engines 
which underwent the trial were, the Rocket, constructed by 
Mr. Stephenson; the Sanspariel, by Hackworth; and the 
Novelty, by Messrs. Braithwait and Ericson. Of these, 
the Rocket obtained the premium. A line of railway was 
selected for the trial, on a level piece of road about two 
miles in length, near a place called Rainhill, between Liver- 
pool and Manchester ; the distance between the two stations 
was a mile and a half, and the engine had to travel this dis- 
tance backwards and forwards ten times, which made alto- 
gether a journey of 30 miles. The Rocket performed this 
journey twice : the first time in 2 hours 14 minutes and 8 
seconds ; and the second time, in 2 hours 6 minutes and 49 
seconds. Its speed at different parts of the journey varied : 
its greatest rate of motion was rather above 29 miles an 
hour; and its least, about 11 1-2 miles an hour. The ave- 
rage rate of the one journey was 13 4-10 miles an hour ; and 
of the other, 14 2-20 miles. This was the only engine which 
performed the complete journey proposed, the others hav- 
ing been stopped from accidents which occurred to them in 
the experiment. The Sanspariel performed the distance be- 
tween the stations eight times, travelling 22 1-2 miles in 1 
hour 37 minutes and 16 seconds. The greatest velocity to 
which this engine attained was something less than 23 miles 
per hour. The Novelty had only passed twice betw T een the 
stations when the joints of the boiler gave way, and put an 
end to the experiment. 

(S8. ) The great object to be attained in the construction 
of these engines was, to combine with sufficient lightness the 
greatest possible heating power. The fire necessarily acts 
on the water in two ways: first, by its radiant heat ; and, 
second, by the current of heated air which is carried by the 
draft through the fire, and finally passes into the chimney. 
To accomplish this object, therefore, it is necessary to expose 
to both these sources of heat the greatest possible quantity 
of surface in contact with the water. These ends were 



LOCOMOTIVE ENGINES ON RAILWAYS. 



171 



attained by the following admirable arrangement in the 
Rocket : — 

This engine is represented in fig. 55. It is supported on 
four wheels • the principal part of the weight being thrown 




on one pair, which are worked by the engine. The boiler 
consists of a cylinder 6 feet in length, w 7 ith flat ends ; the 
chimney issues from one end, and to the other end is attach- 
ed a square box, b, the bottom of which is furnished with the 
grate on which the fuel is placed. This box is composed of 
two casings of iron, one contained within the other, having 
between them a space about 3 inches in breadth ; the mag- 
nitude of the box being 3 feet in length, 2 feet in width, and 
3 feet in depth. The casing which surrounds the box com- 
municates with the lower part of the boiler by a pipe marked 
c ; and the same casing at the top of the box communicates 
with the upper part of the boiler by another pipe marked 
d. When water is admitted into the boiler, therefore, it 



172 



THE STEAM ENGINE. 



Fig. 5C. 




flows freely through the pipe c, into the casing- which sur- 
rounds the furnace or fire-box, and fills this casing to the 
same level as that which it has in the boiler. When the en- 
gine is at work, the boiler is kept about half filled with wa- 
ter; and, consequently, the casing surrounding the furnace 
is completely filled. The steam which is generated in the 
water contained in the casing finds its exit through the pipe 
d, and escapes into the upper part of the boiler. A section 
of the engine, taken at right angles to its length is represent- 
ed at fig. 56. Through the lower part of 
the boiler pass a number of copper tubes 
of small size, which communicate at one 
end with the fire-box, and at the other 
with the chimney, and form a passage 
for the heated air from the furnace to 
the chimney. The ignited fuel spread 
on the grate at the bottom of the fire- 
box disperses its heat by radiation, and acts in this manner 
on the whole surface of the casing surrounding the fire-box; 
and thus raises the temperature of the thin shell of water 
contained in that casing. The chief part of the water in the 
casing, being lower in its position than the water in the boil- 
er, acquires a tendency to ascend when healed, and passes 
into the boiler ; so that a constant circulation of the heated 
water is maintained, and the water in the boiler must neces- 
sarily be kept at nearly the same temperature as the water 
in the casing. The air which passes through the burning 
fuel, and which fills the fire-box, is carried by the draft 
through the tubes which extend through the lower part of 
the boiler; and as these tubes are surrounded on every side 
with the water contained in the boiler, this air transmits its 
heat through these tubes to the water. It finally issues into 
the chimney, and rises by the draft. The power of this fur- 
nace must necessarily depend on the power of draft in the 
chimney ; and to increase this, and at the same time to dis- 
pose of the waste steam after it has worked the piston, this 



LOCMOTIVE ENGINES ON RAILWAYS. 173 

steam is carried off by a pipe l, which passes from the cylin- 
der to the chimney, and escapes there in a jet which is turn- 
ed upwards. By thevelocity with which it issues from this 
jet, and by its great comparative levity, it produces a strong 
current upwards in the chimney, and thus gives force to the 
draft of the furnace. In fig. 56. the grate-bars are represent- 
ed at the bottom of the fire-box at r. There are two cylin- 
ders, one of which works each wheel ; one only appearing 
in the drawing, fig. 55., the other being concealed by the en- 
gine. The spokes which these cylinders work are placed at 
right angles on the wheels ; the wheels being fixed on a com- 
mon axle, with which they turn. 

In this engine, the surface of water surrounding the fire- 
box, exposed to the action of radiant heat, amounted to 20 
square feet, which received heat from the surface of 6 square 
feet of burning fuel on the bars. The surface exposed to 
the action of the heated air amounted to 118 square feet. 
The engine- drew after it another carriage, containing fuel 
and water; the fuel used was coke, for the purpose of avoid- 
ing the production of smoke. 

(89.) The Sanspareil of Mr. Hackworth is represented in 
fig. 57. ; the horizontal section being exhibited in fig. 58. 

The draft of the furnace is produced in the same manner 
as in the Rocket, by ejecting the waste steam coming from 
the cylinder into the chimney ; the boiler, however, differs 
considerably from that of the Rocket. A recurved tube 
passes through the boiler, somewhat similar to that already 
described in the early engine of Messrs. Trevithick and 
Vivian. In the horizontal section (fig. 58.), d expresses 
the opening of the furnace at the end of the boiler, beside 
the chimney. The grate-bars appear at a, supporting the 
burning fuel; and a curved tube passing through the boiler, 
and terminating in the chimney, is expressed at b, the direc- 
tion of the draft being indicated by the arrow; c is a section 
of the chimney. The cylinders are placed, as in the Rocket, 
on each side of the boiler; each working a separate wheel, 



174 



THE STEAM ENGINE. 



but acting on spokes placed at right angles to eaeh other. 
The tube in which the grate and flue are placed diminishes 
in diameter as it approaches the chimney. At the mouth 
where the grate was placed, its diameter was 2 feet; and it 
was gradually reduced, so that, at the chimney, its diameter 
was^only 15 inches. The grate-bars extended 5 feet into 
the tube. The surface of water exposed to the radiant heat 



ivvyvj 




LOCOMOTIVE ENGINES ON RAILWAYS. 



175 



of the fire was 16 square feet; and that exposed to the ac- 
tion of the heated air and flame was about 75 square feet. 
The magnitude of the grate or sheet of burning fuel which 
radiated heat, was 10 square feet. 

(90.) The Novelty, of Messrs. Braithwait and Ericson, 
is represented in fig. 59.; and a section of the generator and 
boiler is exhibited in fig. 60.: the corresponding parts in the 
two figures are marked by the same letters. 




A is the generator or receiver, containing the steam which 
works the engine; this communicates with a lower genera- 
tor, b, which extends in a horizontal direction the entire 
length of the carriage. Within the generator, a, is contain- 
ed the furnace, f, which communicates in a tube, c; carried 
up through the .generator, and terminated at the top by 
sliding shutters, which exclude the air, and which are only 
opened to supply fuel to the grate, f. Below the grate the 
furnace is not open, as usual, to the atmosphere, but commu- 
nicates by a tube, e, with a bellows, d; which is worked by 
the engine, and which forces a constant stream of air, by the 
tube e, through the fuel on f, so as to keep that fuel in vivid 
combustion. The heated air, contained in the furnace, f, 
is driven on, by the same force, through a small curved tube 
marked e, which circulates like a worm (as represented in 
fig. 60.) through the horizontal generator or receiver; and, 
tapering gradually, until reduced to very small dimensions, 



176 



THE STEAM ENGINE. 



it finally issues into the chimney, g. The air, in passing 
along this tube, imparts its heat to the water by which the 
tube is surrounded, and is brought to a considerably reduced 




temperature when discharged into the chimney. The cy- 
linder, which is represented at k, works one pair of wheels, 
by means of a bell-crank; the other pair, when necessary, 
being connected with them. 

In this engine, the magniiude of the surface of burning 
fuel on the grate-bars is less than 2 square feet; the surface 
exposed to radiant heat is 9§ square feet ; and the surface of 
water exposed to heated air is about 33 square feet. 

The superiority of the Rocket may be attributed chiefly 
to the greater quantity of surface of the water which is ex- 
posed to the action of the fire. With a less extent of grate- 
bars than the Sanspareil, in the proportion of 3 to 5, it ex- 
poses a greater surface of water to radiant heat, in the pro- 
portion of 4 to 3 ; and a greater surface of water to heated 
air, in the proportion of more than 3 to 2. It was found. that 
the Rocket, compared with the Sanspareil, consumed fuel, 
in the evaporation of a given quantity of water, in the pro- 
portion of 11 to 28. The suggestion of using the tubes to 
conduct through the water the heated air to the chimney is 
due to Mr. Booth, treasurer of the Liverpool and Manches- 
ter Railway Company; and, certainly, nothing has been more 
conducive to the efficiency of the engines since used than this 
improvement. It is much to be regretted that the ingenious 



' LOCOMOTIVE ENGINES ON RAILWAYS. 177 

gentleman who suggested this has reaped none of the advan- 
tages to which a patentee would be legally entitled.* 

(91.) The great object to be effected in the boilers of these 
engines is, to keep a small quantity of water at an excessive 
temperature, by means of a small quantity of fuel kept in the 
most active state of combustion. To accomplish this, it is 
necessary, first, so to shape the boiler, furnace, and flues, 
that the water shall be in contact with as extensive a surface 
as possible, every part of which is acted on either imme- 
diately, by the heat radiating from the fire, or mediately, by 
the air which has passed through the fire, and which finally 
rushes into the chimney: and, secondly, that such a forcible 
draught should be maintained in the furnace, that a quantity 
of heat shall be extricated from the fuel, by combustion, suf- 
ficient to maintain the water at the necessary temperature, 
and to produce the steam with sufficient rapidity. To ac- 
complish these objects, therefore, the chamber containing 
the grate should be completely surrounded by water, and 
should be below the level of the water in the boiler. The 
magnitude of the surface exposed to radiation should be as 
great as is consistent with the whole magnitude of the ma- 
chine. The comparative advantage which the Rocket pos- 
sessed in these respects over the other engines will be evi- 
dent on inspection. In the next place, it is necessary that 
the heat, which is absorbed by the air passing through the 
fuel, and keeping it in a state of combustion, should be trans- 
ferred to the water before the air escapes into the chimney. 
Air being a bad conductor of heat, to accomplish this it is 
necessary that the air in the flues should be exposed to as 
great an extent of surface in contact with the water as possi- 
ble. No contrivance can be less adapted for the attainment 
of this end than one or two large tubes traversing the boiler, 
as in the earliest locomotive engines: the body of air which 

* Ml-. Booth received a part of the premium of 500/., but has not 
participated in any degree in the profits of the manufacture of the 
engines. 

23 



178 THE STEAM ENGINE. 

passes through the centre of these tubes had no contact with 
their surface, and, consequently, passed into the chimney 
at nearly the same temperature as that which it had when it 
quitted the fire. The only portion of air which imparted its 
heat to the water was that portion which passed next to the 
surface of the tube. 

Several methods suggest themselves to increase the sur- 
face of water in contact with a given quantity of air passing 
through it. This would be accomplished by causing the air 
to pass between plates placed near each other, so as to 
divide the current into thin strata, having between them 
strata of water, or it might be made to pass between tubes 
differing slightly in diameter, the water passing through an 
inner tube, and being also in contact with the external sur- 
face of the outer tube. Such a method would be similar in 
principle to the steam-jacket used in Wattfs steam engines, 
or to the condenser of Cartwrighfs engine already de- 
scribed. But, considering the facility of constructing small 
tubes, and of placing them in the boiler, thai method, per- 
haps, is, on the whole, the best in practice; although the 
shape of a tube, geometrically considered, is most unfavour- 
able for the exposure of a fluid contained in it to its surface. 
The air which passes from the fire-chamber, being subdivided 
as it passes through the boiler by a great number of very 
small tubes, may be made to impart all its excess of heat to 
the water before it issues into the chimney. This is all 
which the most refined contrivance can effect. The Rocket 
engine was traversed by 25 tubes, each 3 inches in diameter; 
and the principle has since been carried to a much greater 
extent. 

The abstraction of a great quantity of heat from the air 
before it reaches the chimney is attended with one conse- 
quence, which, at first view* would present a difficulty ap- 
parently insurmountable; the chimney would, in fact, lose 
its power of draught. This difficulty, however, was re- 
moved by using the waste steam, which had passed from 



LOCOMOTIVE ENGINES ON RAILWAYS. 179 

the cylinder alter working the engine, for the purpose of 
producing a draught. This steam was urged through a jet 
presented upwards in the chimney, and driven out with 
such force in that direction as to create a sufficient draught 
to work the furnace. 

It will be observed that the principle of draught in the 
Novelty is totally distinct from this: in that engine the 
draught is produced by a bellows worked by the engine. 
The question, as far as relates to these two methods, is, 
whether more power is lost in supplying the steam through 
the jet, as in the Rocket, or in working the bellows, as in 
the Novelty. The force requisite to impel the steam 
through the jet must be exerted by the returning stroke of 
the piston, and, consequently, must rob the working effect 
to an equivalent amount. On the other hand, the power 
requisite to work the bellows in the Novelty must be sub- 
ducted from the available power of'the engine. The former 
method is found to-be the more effectual and economical. 

The importance of these details will be understood, when 
it is (considered that the only limit to the attainment of speed 
by locomotive engines is the power to produce in a given 
time a certain quantity of steam. Each stroke of the piston 
causes one revolution of the wheels, and consumes two cy- 
linders full of steam: consequently, a cylinder of steam cor- 
responds to a certain number of feet of road travelled over: 
hence it is that the production of a rapid and abundant sup- 
ply of heat, and the imparting of that heat quickly and effec- 
tually to the water, is the key to the solution of the problem 
to construct an engine capable of rapid motion. 

The method of subdividing the flue into lubes was carried 
much further by Mr. Stephenson after the construction of 
the Rocket ; and, indeed, the principle was so very obvious, 
that it is only surprising that, in the first instance, tubes of 
smaller diameter than 3 inches were not used. In engines 
since constructed, the number of tubes vary from 90 to 120, 
the diameter being reduced to 2 inches or less, and in some 



180 



THE STEAM ENGINE. 



instances tabes have been introduced, even to the number of 
150, of H inch diameter. In the Meteor, 20 square feet 
are exposed to radiation, and 139 to the contact of heated 
air; in the Arrow, 20 square feet to radiation, and 145 to the 
contact of heated air. The superior economy of fuel gained 
by this means will be apparent by inspecting the following 
table, which exhibits the consumption of fuel which was re- 
quisite to convey a ton weight a mile in each of four engines, 
expressing also the rate of the motion: — 





Average rate of 


Consumption of 


Engines. 


speed in miles 


- Coke in pounds 




per hour. 


per ton per mile. 


No. 1. Rocket 


14 


2-41 


2. Sanspareil 


15 


2-47 


3. Phoenix 


12 


1-42 


4. Arrow 


12 


1-25 



(92.) Since the period' at which the railway was opened 
for the actual purposes of transport, the locomotive engine3 
have been in a state of progressive improvement. Scarcely 
a month has passed without suggesting some change in the 
details, by which fuel might be economised, the production 
of steam rendered more rapid, the wear of the engine ren- 
dered slower, the proportionate strength of the different 
parts improved, or some other desirable end obtained. The 
consequence of this has been, that the particular engines to 
which we have alluded, and others of the same class, with- 
out having, as it were, lived their natural life, or without 
having been worn out by work, have been laid aside to give 
place to others of improved powers. By the exposure of 
the cylinders to the atmosphere in the Rocket, and engines 
of a similar form, a great waste of heat was incurred, and it 
was accordingly determined to remove them from the exte- 
rior of the boiler, and to place them within a casing imme- 
diately under the chimney: this chamber was necessarily 
kept warm by its proximity to the end of the boiler, but 
more by the current of heated air which constantly rushed 



LOCOMOTIVE ENGINES ON RAILWAYS. 181 

into it from the tubes. This change, also, rendered neces- 
sary another, which improved the working of the engine. 
In the earlier engines the motion of the piston was commu- 
nicated to the wheel by.a connecting rod attached to one of 
the spokes on the exterior of the wheel, as represented in 
fig. 55. By the change to which we have just alluded, the 
cylinders being placed between the wheels under the chim- 
ney, this mode of working became inapplicable, and it was 
considered better to connect the piston-rods with two cranks 
placed at right angles on the axles of the great wheels. By 
this means, it was found that the working of the machine 
was more even, and productive of less strain than in the 
former arrangement. On the other hand, a serious disad- 
vantage was incurred by the adoption of a cranked axle. 
The weakness necessarily arising from such a form of axle 
could only be counterbalanced by great thickness and weight 
of metal; and even this precaution does not prevent the oc- 
casional fracture of such axles at the angles of the cranks. 
The advantages, however, of this plan, on the whole, are 
considered to predominate. 

In the most improved engines in present use two safety- 
valves are provided, of which only one is in the power of 
the engine-man. The tubes being smaller and more numer- 
ous than in the earlier engines, the heat is more completely 
extracted from the air before it enters the chimney. A 
powerful draft is rendered still more necessary by the small- 
ness of the tubes: this is effected by forcing the steam 'which 
has worked the pistons through a contracted orifice, pre- 
sented upwards in the chimney, by the regulation of which 
any degree of draft may be obtained. 

One of the most improved engines at present in use is re- 
presented in fig. 61. 

a represents the cylindrical boiler, the lower half of which 
is traversed by tubes, as described in the Rocket. They 
are usually from SO to 100 in number, and about 1§ inch in 
diameter; the boiler is about 7 feet in length; the fire-cham- 



182 



THE STEAM ENGINE. 



raf 




ber is attached to one end of it, at f, as in the Rocket, and 
similar in construction ; the cylinders are inserted in a cham- 
ber at the other end, immediately under the chimney. The 
piston-rods are supported in the horizontal position by 
guides; and connecting rods extend from them, under the 
engine, to the two cranks placed on the axle of the large 
wheels. The effects of any inequality in the road are coun- 
teracted by springs, on which the engine rests; the springs 
being below the axle of the great wheels, and above that of 
the less. The steam is supplied to the cylinders, and with- 
drawn, by means of the common sliding valves, which are 
worked by an eccentric wheel placed on the axle of the large 
wheels of the carriage. The motion is communicated from 
this eccentric wheel to the valve by sliding rods. The stand 
is placed for the attendant at the end of the engine, next the 
fire-place, f; and two levers, l, project from the end, which 
communicate with the valves by means of rods, by which 
the engine is governed, so as to stop or reverse the motion. 
The wheels of these engines have been commonly con- 
structed of wood, with strong iron tires, furnished with flanges 
adapted to the rails. But Mr. Stephenson has recently sub- 



LOCOMOTIVE ENGINES ON RAILWAYS. 183 

stituted, in some instances, wheels of iron with hollow 
spokes. The engine draws after it a tender carriage contain- 
ing the fuel and water ; and, when carrying a light load, is 
capable of performing the whole journey from Liverpool to 
Manchester without a fresh supply of water. When a heavy 
load of merchandise is drawn, it is usual to take in water at 
the middle of the trip. 

(93.) In reviewing all that has been stated, it will be per- 
ceived that the efficiency of the locomotive engines used on 
this railway is mainly owing to three circumstances : 1st, 
The unlimited power of draft in the furnace, by projecting 
the waste steam into the chimney ; 2d, The unlimited ab- 
straction of heat from the air passing from the furnace, by 
Mr. Booth's ingenious arrangement of tubes traversing the 
boiler; and, 3d, Keeping the cylinders warm, by immers- 
ing them in the chamber under the chimney.* There are 
many-minor details which might be noticed with approba- 
tion, but these constitute the main features of the improve- 
ments, and should never, for a moment, be lost sight of by 
projectors of locomotive engines. 

The successive introduction of improvements in tne en- 
gines, some of which we have mentioned, has been accom- 
panied by corresponding accessions to their practical power, 
and to the economy of fuel ; and they have now arrived at a 
point which is as far beyond the former expectations of the 
most sanguine locomotive projectors, as it assuredly is short 
of the perfection of which these wonderful machines are still 
susceptible. 

In the spring of the year 1832, 1 made several experi- 
ments on the Manchester railway, with a view to determine, 
in the actual state of the locomotive engines at that time, 
their powers with respect to the amount of load and the eco- 

* Mr. Robert Stephenson, whose experience and skill in the construc- 
tion of locomotives . attaches great importance to this condition. It has 
lately, however, been abandoned by some other engine makers, for the 
purpose of getting rid of the cranked axle which must accompany it. 



184 THE STEAM ENGINE. 

nomy of fuel. Since that time I am not aware that, in these 
respects, the engine has received any material improvement. 
The following are the particulars of three experiments thus 
made : — 



On Saturday, the 5th of May, the engine called the e Vic- 
tory" took 20 wagons of merchandise, weighing gross 92 
tons 19 cwt. 1 qr., together with the tender containing fuel 
and water, of the weight of which T have no account, from 
Liverpool to Manchester (30 miles,) in 1 h. 34 min. 45 sec. 
The train stopped to take in water half-way, for 10 minutes, 
not included in the above mentioned time. On the inclined 
plane rising 1 in 96, and extending 1^ mile, the engine was 
assisted by another engine called the " Samson," and the as- 
cent was performed in 9 minutes. At starting, the fire- 
place was well filled with coke, and the coke supplied to the 
tender accurately weighed. On arriving at Manchester the 
fire-place was again filled, and the coke remaining in the 
tender weighed. The consumption was found to amount to 
929 pounds net weight, being at the rate of one third of a 
pound per ton per mile. 

Speed on the level was 18 miles an hour ; on a fall of 4 
feet in a mile, 21^ miles an hour ; fall of 6 feet in a mile, 
25§ miles an hour ; on the rise over Chatmoss, 8 feet in a 
mile 17| miles an hour ; on level ground sheltered from the 
wind, 20 miles an hour. The wind was moderate, but di- 
rect ahead. The working wheels slipped three times on Chat- 
moss, and the train was retarded from 2 to 3 minutes. 

The engine, on this occasion, was not examined before or 
after the journey, but was presumed to be in good working 
order. 

II. 

On Tuesday, the 8th of May, the same engine performed 
the same journey, with 20 wagons, weighing gross 90 tons 



LOCOMOTIVE ENGINES ON RAILWAYS. 185 

7 cwt. 2 qrs., exclusive of the unascertained weight of the 
tender. The time of the journey was 1 b. 41 min. The 
consumption of coke 1040 lbs. net weight, estimated as be- 
fore. Rate of speed : — 

Level - - 17| miles per hour. 

Fall of 4 feet in a mile 22 

6 - - - 22h 

Rise of S - - - 15 
On this occasion there was a high wind ahead on the quar- 
ter, and the connecting rod worked hot, owing to having 
been keyed too tight. On arriving at Manchester, I caused 
the cylinders to be opened, and found that the pistons were 
so loose, that the steam blew through the cylinders with 
great violence. By this cause, therefore, the machine was 
robbed of a part of its power during the journey j and this 
circumstance may explain the slight decrease in speed, and 
increase in the consumption of fuel, with a lighter load in 
this journey compared with that performed on the 5th of 
May. 

The Victory weighs 8 tons 2 cwt., of which 5 tons 4 cwt. 
rest on the drawing wheels. The cylinders are 11 inches 
diameter, and 16 inches stroke; and the diameter of the 
drawing wheels is 5 feet. 

III. 

On the 29th of May, the engine called the " Samson," 
(weighing 10 tons 2 cwt., with 14-inch cylinders, and 16- 
inch stroke ; wheels 4 feet 6 inches diameter, both pairs be- 
ing worked by the engine ; steam 50 lbs. pressure, 130 tubes) 
was attached to 50 wagons, laden with merchandise ; net 
weight about 150 tons; gross weight, including wagons, ten- 
der, &c, 223 tons 6 cwt. The engine with this load travel- 
led from Liverpool to Manchester (30 miles) in 2 h. and 40 
min., exclusive of delays upon the road for watering, &c, 
being at the rate of nearly 12 miles an hour, The speed va- 

24 



186 THE STEAM ENGINE. 

ried according to the inclinations of the road. Upon a level, 
it was 12 miles an hour ; upon a descent of 6 feet in a mile, 
it was 16 miles an hour: upon a rise of 8 feet in a mile, it 
was about 9 miles an hour. The weather was calm, the 
rails very wet ; but the wheels did not slip, even in the 
slowest speed, except at starting, the rails being at that place 
soiled and greasy with the slime and dirt to which they are 
always exposed at the stations. The coke consumed in this 
journey, exclusive of what was raised in getting up the steam, 
was 1762 lbs., being at the rate of a quarter of a pound per 
ton per mile. 

(94.) From the above experiments it appears that a loco- 
motive engine, in good working order, with its full comple- 
ment of load, is capable of transporting weights at an ex- 
pense in fuel amounting to about 4 ounces of coke per ton 
per mile. The attendance required on the journey is that of 
an engine-man and a fire-boy ; the former being paid Is. 6c?. 
for each trip of 30 miles, and the latter Is. In practice, 
however, we are to consider, that it rarely happens that the 
full complement of load can be sent with the engines ; and 
when lesser loads are transported, the proportionate expense 
must for obvious reasons, be greater. 

The practical expenditure of fuel on the Liverpool and 
Manchester line may, perhaps, be fairly estimated at half a 
pound of coke per ton per mile. 

(95.) Having explained the power and efficiency of these 
locomotive engines, it is now right to notice some of the 
defects under which they labour. 

The great original cost, and the heavy expense. of keep- 
ing the engines used on the railway in repair, have pressed 
severely on the resources of the undertaking. One of the 
best constructed of the later engines costs originally about 
800/. It may be hoped that, by the excitement of competi- 
tion, the facilities derived from practice, and from the manu- 
facture of a greater number of engines of the same kind, 
some reduction of this cost may be effected. The original 



LOCOMOTIVE ENGINES ON RAILWAYS. 187 

cost, however, is far from being the principal source of ex- 
pense: the wear and tear of these machines, and the occa- 
sional fracture of those parts on which the greatest strain has 
been laid, have greatly exceeded what the directors had an- 
ticipated. Although this source of expense must be in part 
attributed to the engines not having yet attained that state 
of perfection, in the proportion and adjustment of their parts, 
of which they are susceptible, and to which experience alone 
can lead, yet there are some obvious defects which demand 
attention. 

The heads of the boilers are flat, and formed of iron, 
similar to the material of the boilers themselves. The tubes 
which traverse the boiler were, until recently, copper, and 
so inserted into the flat head or ends as to be water-tight. 
When the boiler is heated, the tubes are found to expand in 
a greater degree than the other parts of the boiler ; which 
frequently causes them either to be loosened at the extremi- 
ties, so as to cause leakage, or to bend from want of room 
for expansion. The necessity of removing and refastening 
the tubes causes, therefore, a constant expense. 

It will be recollected that the fire-place is situated at one 
end of the boiler, immediately below the mouths of the 
tubes: a powerful draught of air, passing through the fire, 
carries with it ashes and cinders, which are driven violently 
through the tubes, and- especially the lower ones, situated 
near the fuel. These tubes are, by this means, subject to 
rapid wear, the cinders continually acting upon their in- 
terior surface. After a short time it becomes necessary to 
replace single tubes, according as they are found to be worn, 
by new ones; and it not unfrequently happens, when this 
is neglected, that tubes burst. After a certain length of time 
the engines require new tubing, which is done at the expense 
of about 70/., allowing for the value of the old tubes. This 
wear of the tubes might possibly be avoided by constructing 
the fire-place in a lower position, so as to be more removed 
from their mouths; or, still more effectually, by interposing 



188 THE STEAM ENGINE. 

a casing of metal, which might be filled with water, between 
the fire-place and those tubes which are the most exposed to 
the cinders and ashes. The unequal expansion of the tubes 
and boilers appears to be an incurable defect, if the present 
form of the engine be retained. If the fire-place and chim- 
ney could be placed at the same end of the boiler, so that 
the tubes might be recurved, the unequal expansion would 
then produce no injurious effect; but it would be difficult 
to clean the tubes if they were exposed, as they are at pre- 
sent, to the cinders. The next source of expense arises 
from the wear of the boiler-head, which is exposed to the 
action of the fire. These require constant patching and fre- 
quent renewal. 

A considerable improvement has lately been .introduced 
into the method of tubing, by substituting brass for copper 
tubes. We are not aware that the cause of this improve- 
ment has been discovered; but it is certain, whatever be the 
cause, that brass tubes are subject to considerably slower 
wear than copper. 

It has been said by some whose opinions are adverse to 
the advantage of railways, but more especially to the parti- 
cular species of locomotive engines now under consideration, 
that the repairs of one of these engines cost so great a sum 
as 1500/. per annum, and that the directors now think of 
abandoning them, or adopting either stationary engines or 
horse power. As to the first of these statements I must 
observe, that the expense of repairs of such machines should 
never be computed in reference to time, but rather to the 
work done, or the distance travelled over. I have ascer- 
tained that engines frequently travel a distance of from 
25,000 to 30,000 miles before they require new tubing. 
During that work, however, single tubes are, of course, oc- 
casionally renewed, and other repairs are made, the expense 
of which may safely be stated as under the original cost of 
the engine. The second statement, that the company con- 
template substituting stationary engines, or horses, for loco- 



LOCOMOTIVE ENGINES ON RAILWAYS. 189 

motives, is altogether at variance with the truth. Whatever 
improvements may be contemplated in locomotives, the 
directors assuredly have not the slightest intention of going 
back in the progress of improvement, in the manner just 
mentioned. 

The expense of locomotive power having so far exceeded 
what was anticipated at the commencement of the under- 
taking, it was thought advisable, about the beginning of 
the year 1834, to institute an inquiry into the causes which 
produced the discrepancy between the estimated and actual 
expenses, with a view to the discovery of some practical 
means by which they could be reduced. The directors of 
the company, for this purpose, appointed a sub-committee 
of their own body, assisted by Mr. Booth, their treasurer, 
to inquire and report respecting the causes of the amount of 
this item of their expenditure, and to ascertain whether any 
and what measures could be devised for the attainment of 
greater economy. A very able and satisfactiory report was 
made by this committee, or, to speak more correctly by 
Mr. Booth. 

It appears that, previous to the establishment of the rail- 
way, Messrs. Walker and Rastrick, engineers, were em- 
ployed by the company to visit various places where steam 
power was applied on railways, for the purpose of forming 
an estimate of the probable expense of working the railway 
by locomotive and by fixed power. These engineers re- 
commended the adoption of locomotive power, and their esti- 
mate was, that the transport might be effected at the rate of 
.278 of a penny, or very little more than a farthing per ton 
per mile. In the year 1833, five years after this investiga- 
tion took place, it was found that the actual cost was .625 
of a penny, or something more than a halfpenny per ton 
per mile, being considerably above double the estimated 
rate. Mr. Booth very properly directed his inquiries to 
ascertain the cause of this discrepancy, by comparing the 
various circumstances assumed by Messrs. Walker and 



190 THE STEAM ENGINE. 

Rastrick, in making their estimate, with those under which 
the transport was actually effected. The first point of dif- 
ference which he observed was the speed of transport: the 
estimate was founded on an assumed speed of ten miles an 
hour, and it was stated that a four-fold speed would require 
an addition of 50 per cent, to the power, without taking 
into account wear and tear. Now the actual speed of trans- 
port being double the speed assumed in the statement, Mr. 
Booth holds it to be necessary to add 25 per cent on that 
score. 

The next point of difference is in the amount of the loads: 
the estimate is" founded upon the assumption, that every en- 
gine shall start with its full complement of load, and that 
with this it shall go, the whole distance. "The facts, how- 
ever, are/' says Mr. JBooth, " that, instead of a full load of 
profitable carriage from Manchester, about half the wagons 
come back empty, and, instead of the tonnage being convey- 
ed the whole way,' ? many thousand tons are conveyed only 
half the way; also, instead of the daily work being uniform, 
it is extremely fluctuating." It is further remarked, that in 
order to accomplish the transport of goods from the branches 
and from intermediate places, engines are despatched several 
times a day, from both ends of the line, to clear the road ; 
the object of this arrangement being rather to lay the foun- 
dation of a beneficial intercourse in future, than with a view 
to any immediate profit. Mr. Booth makes a rough esti- 
mate of the disadvantages arising from these circumstances 
by stating them at 33 per cent, in addition to the original 
estimate. 

The next point of difference is the fuel. In the original 
estimate coal is assumed as the fuel, and it is taken at the 
price of five shillings and tenpence per ton: now the act of 
parliament forbids the use of coal which would produce 
smoke; the company have, therefore, been obliged to use 
coke, at seventeen shillings and sixpence a ton. Taking 



LOCOMOTIVE ENGINES ON RAILWAYS. 191 

coke, then, to be equivalent to coal, ton for ton, this would 
add .162 to the original estimate. 

These several discrepancies being allowed for, and a pro- 
portional amount being added to the original estimate, the 
amount would be raised to .601 of a penny per ton per mile, 
which is within one fortieth of a penny of the actual cost. 
This difference is considered to be sufficiently accounted for 
by the wear and tear produced by the very rapid motion, 
more especially when it is considered that many of the en- 
gines were constructed before the engineer was aware of the 
great speed that would be required. 

" What then," says Mr. Booth, in the Report already 
alluded to, " is the result of these opposite and mutually 
counteracting circumstances ? and what is the present posi- 
tion of the company in respect of their moving power? Sim- 
ply, that they are still in a course of experiment, to ascertain 
practically the best construction, and the most durable mate- 
rials, for engines required to transport greater weights, and 
at greater velocities, than had, till very recently, been con- 
sidered possible; and which, a few years ago, it had not en- 
tered into the imagination of the most daring and sanguine 
inventor to conceive: and, farther, that these experiments 
have necessarily been made, not with the calm deliberation 
and quiet pace which a salutary caution recommends, — 
making good each step in the progress of discovery before 
advancing another stage, — but amidst the bustle and respon- 
sibilities of a large and increasing traffic; the directors being 
altogether ignorant of the time each engine would last before 
it would be laid up as inefficient, but compelled to have en- 
gines, whether good or bad; being ^ware of various defects 
and imperfections, which it was impossible at the time to 
remedy, yet obliged to keep the machines in motion, under 
all the disadvantages of heavy repairs, constantly going on dur- 
ing the night, in order that the requisite number of engines 
might be ready for the morning's work. Neither is this great 
experiment yet complete; it is still going forward. But the 



192 THE STEAM ENGINE. 

most prominent difficulties have been in a great measure sur- 
mounted, and your committee conceive, that they are war- 
ranted in expecting, that the expenditure in this department 
will, ere long, be materially reduced, more especially when 
they consider the relative performances of the engines at the 
present time compared with what it was two yeers ago." 

In the half year ending 31st December, 1831, the six best 
engines performed as follows: — 

m Miles. 

Planet - - - 9,986 

Mercury - - - - 11,040 

Jupiter - - 11,618 

Saturn - - - - 11,786 

Venus - " '* " 12,850 

Etna - - : .- - 8,764 



Making in all - - 66,044 

In the half year ending 31st December, 1833, the six best 
engines performed as follows: — 







Miles. 


Jupiter 


.- 


16,57.2 


Saturn 


- 


- 18,678 


Sun 


. 


15,552 


Etna 


- 


- 17,763 


Ajax 


_ 


11,678 


Firefly 


Making in all 


- 15,608 




- 95,851 



(96.) The advantages derivable from railroads are greatly 
abridged by the difficulty arising from those changes of level 
to which all roads are necessarily liable; but in the case of 
raflroads, from causes peculiar to themselves, these changes 
of level occasion great inconvenience. To explain the nature 
of these difficulties, it will be necessary to consider the rela- 
tive proportion which must subsist between the power of 



LOCOMOTIVE ENGINES ON RAILWAYS. 193 

traction oil a level and on an inclined plane. On a level 
railroad, the force of traction necessary to propel any load, 
placed on wheel carriages of the construction now common- 
ly used, may perhaps be estimated a 7§ pounds,* for every 
ton gross in the load; that is to say, if a load of one ton gross 
were placed upon wheel carriages upon a level railroad, the 
traces of horses drawing it would be stretched with a force 
equivalent to 7J pounds. If the load amounted to two or 
three tons, the tension of the traces would be increased to 
15 or 22^ pounds, and so on. The necessity of this force 
of traction, arising from the want of perfect smoothness in 
the road/and from the friction of the wheels and axles of the 
carriages, must be the same whether the road be level or in- 
clined ; and consequently, in ascending an inclined plane, the 
same force of traction will be necessary in addition to that 
which arises from the tendency of the load to fall down the 
plane. This latter tendency is always in the proportion of 
the elevation of the plane to its length; that is to say, a plane 
which rises 1 foot in 100 will give a weight of 100 tons a 
tendency to fall down the plane amounting to 1 ton, and 
would therefore, add 1 ton to the force of traction necessary 
for such a load on a level. 

Now since 7.4 pounds is very nearly the 300th part of a 
ton, it follows that if an inclination upon a rail-road rises at 
the rate of 1 foot in 300, or, what is the same, 17i feet in a 
mile, such an acclivity will add 74 pounds per ton to the 
force of traction. This acclivity therefore would require a 
force of traction twice as great as a level. In like manner a 
rise of 35 feet in a mile would require three times the force 

* The estimate commonly adopted by engineers at present is 9 pounds 
per ton. I have no dobt, however, that this is too high. I am now 
(November, 1835,) engaged in an extensive course of experiments on 
different railways, with a view to determine with precision this and other 
points connected with the full developement of their theory ; and I have 
reason to believe, from the observations I have already made, that even 
7h pounds per ton is above the average force of traction upon the level. 

25 



194 THE STEAM ENGINE. 

of traction of a level, 524 feet in a mile four times that force, 
and so on. In fact, for every 7 feet in a mile which an ac- 
clivity rises, 3 pounds per ton will be added to the force of 
traction,. If we would then ascertain the power necessary 
to pull a load up any given acclivity upon a railroad, we 
must first take 74 pounds as the force necessary to overcome 
the common resistance of the road, and then add 3 pounds 
for every 7 feet which the acclivity rises per mile. For ex- 
ample, suppose an acclivity to rise at the rate of 70 feet in a 
mile, the force of traction necessary to draw a ton up it 
would be thus calculated : — 

Friction - - - - 74 lbs. 

70 feet =10 times 3 lbs. - 30 



Total force - - - 374 

It will be apparent, therefore, that if a railroad undulates 
by inclined planes, even of the most moderate inclinations, 
the propelling power to be used upon it must be of such a 
nature as to be capable of increasing its intensity in a great 
degree, according to the elevation of the planes which it has 
to encounter. A plane which rises 524 feet per mile pre- 
sents to the eye scarcely the appearance of an ascent, and yet 
requires the power of traction to be increased in a fourfold 
proportion. 

It is the property of animal power, that within certain li- 
mits its energy can be put forth at will, according to the 
exigency of the occasion ; but the intensity of mechanical 
power, in the instance now considered, cannot so conveni- 
ently be varied, except indeed within narrow limits. 

In the application of locomotive engines upon railways the 
difficulty arising from inclined planes has been attempted to 
be surmounted by several methods, which we shall now ex- 
plain. 

1. Upon arriving at the foot of the plane the load is di- 
vided, and the engine carries it up in several successive trips, 
descending the plane unloaded after each trip. The objec- 



LOCOMOTIVE ENGINES ON RAILWAYS. 195 

tion to this method is the delay which it occasions, — a circum- 
stance which is incompatible with a large transport of passen- 
gers. From what has been stated, it would be necessary, when 
the engine is fully loaded on a level, to divide its load into four 
parts, to be successively carried up when the incline rises 52 
feet per mile. This method has been practised in the trans- 
port of merchandise occasionally, when heavy loads were 
carried on the* Liverpool and Manchester line, upon the 
Rainhill incline. 

2. A subsidiary or assistant locomotive engine may be 
kept in constant readiness at the foot of each incline, for the 
purpose of aiding the different trains, as they arrive, in as- 
cending. The objection to this mode is the cost of keeping 
such an engine with its boiler continually prepared, and its 
steam up. It would be necessary to keep its fire continu- 
ally lighted, whether employed or not ; otherwise, when the 
train would arrive at the foot of the incline, it should wait 
until the subsidiary engine was prepared for work. In cases 
where trains would start and arrive at stated times, this ob- 
jection, however, would have less force. This method is at 
present generally adopted on the Liverpool and Manchester 
line. This method, however, cannot be profitably applied 
to planes of any considerable length. 

3. A fixed steam engine may be erected on the crest of 
the incline, so as to communicate by ropes with the train at 
the foot. Such an engine would be capable of drawing up 
one or two trains together, with their locomotives, according 
as they would arrive, and no delay need be occasioned. This 
method requires that the fixed engine should be kept constant- 
ly prepared for work, and the steam continually up in the boil- 
er. This expedient is scarcely compatible with a large tran- 
sit of passengers, except at the terminus of a line. 

4. In working on the level, the communication between 
the boiler and the cylinder in the locomotives may be so re- 
strained by partially closing the throttle valve, as to cause 
the pressure upon the piston to be less in a considerable de- 



196 THE STEAM ENGINE. 

gree than the pressure of steam in the boiler. If under such 
circumstances a sufficient pressure upon the piston can be ob- 
tained to draw the load on the level, the throttle valve may 
be opened on approaching the inclined plane, so as to throw 
on the piston a pressure increased in the same proportion as 
the previous pressure in the boiler was greater than that upon 
the piston. If the fire be sufficiently active to keep up the 
supply of steam in this manner during the ascent, and if the 
rise be not greater in proportion than the power thus obtain- 
ed, the locomotive will draw the load up the incline without 
further assistance. It is, however, to be observed, that in 
this case the load upon the engine must be less than the 
amount which the adhesion of its working wheels with the 
railroad is capable of drawing ; for this adhesion must be 
adequate to the traction of the same load up the incline, other- 
wise whatever increase of power might be obtained by open- 
ing the throttle valve, the drawing wheels would revolve 
without causing the load to advance. This method has been 
generally practised upon the Liverpool and Manchester line 
in the transport of passengers ; and, indeed, it is the only 
method yet discovered, which is consistent with the 'expe- 
dition necessary for that species of traffic. The objections to 
this method are, the necessity of maintaining a much higher 
pressure in the boiler than is sufficient for the purposes of the 
load upon more level parts of the line. 

In the practice of this method considerable aid may be 
derived also by suspending the supply of feeding water during 
the ascent. It will be recollected that a reservoir of cold 
water is placed in the tender which follows the engine, and 
that the water is driven from this reservoir into the boiler 
by a forcing pump, which is worked by the engine itself. 
This pump is so constructed that it will supply as much 
cold water as is equal to the evaporation, so as to maintain 
constantly the same quantity of water in the boiler. But it 
is evident, on the other hand, that the supply of this water 
has a tendency to check the rate of evaporation, since in 



LOCOMOTIVE ENGINES ON RAILWAYS. 197 

being raised to the temperature of the water with which it 
mixes, it must absorb a considerable portion of the heat 
supplied by the fire. With a view to accelerate the produc- 
tion of steam, therefore, in ascending the inclines, the en- 
gine-man may suspend the action of the forcing pump, and 
thereby stop the supply of cold water to the boiler; the 
evaporation will go on with increased rapidity, and the ex- 
haustion of water produced by it will be repaid by the 
forcing pump on the next level, or still more effectually on 
the next descending incline. Indeed the feeding pump may 
be made to act in descending an incline if necessary, when 
the action of the engine itself is suspended, and when the 
train descends by its own gravity, in which case it will per- 
form the part of a brake upon the descending train. 

This method, on railroads intended for passengers, may be 
successfully applied on inclines which do not exceed 18 
feet in a mile; and, with a sacrifice of the expense of loco- 
motive power, inclines so steep as 36 feet in a mile may be 
worked in this manner. As, however, the sacrifice is con- 
siderable, it will, perhaps, be always better to work the 
more steep inclines by assistant engines. 

5. The mechanical connexion, between the piston of the 
cylinder and the points of contact of the working wheels 
with the road may be so altered, upon arriving at the incline, 
as to give the piston a greater power over the working 
•wheels. This may be done in ah infinite variety of ways, 
but hitherto no method has been suggested sufficiently sim- 
ple to be applicable in practice; and even were any means 
suggested which would accomplish this, unless the intensity 
of the impelling power were at the same time increased, it 
would necessarily follow that the speed of the motion would 
be diminished in exactly the same proportion as the power 
of the piston over the working wheels would be increased. 
Thus, on the inclined plane, which rises 55 feet per a mile, 
upon the Liverpool line, the speed would be diminished to 
nearly one fourth of its amount upon the level. 



198 THE STEAM ENGINE. 

Whatever be the method adopted to surmount inclined 
planes upon a railway, inconvenience attends the descent 
upon them. The motion down the incline by the force of 
gravity is accelerated; and if the train be not retarded, a 
descent of any considerable length, even at a small elevation, 
would produce a velocity which would be attended with 
great danger. The shoe used to retard the descent down 
hills on turnpike roads cannot be used upon railroads, and 
the application of brakes to the faces of the wheels is like- 
wise attended with some uncertainty. The friction produced 
by the rapid motion of the wheel sometimes sets fire to wood, 
and iron would be inadmissible. The action of the steam 
on the piston may be reversed, so as to oppose the motion 
of the wheels; but even this is attended with peculiar dif- 
ficulty. 

From all that has been stated, it will be apparent that, 
with our present knowledge, considerable inclines are fatal 
to the profitable performance on a railway, and even small 
inclinations are attended with great inconvenience.* 

(97.) To obtain from the locomotive steam engines now 
used on the railway the most powerful effects, it is necessary 
that the load placed on each engine should be very conside- 
rable. It is not possible, with our present knowledge, to 
construct and work three locomotive engines of this kind, 
each drawing a load of 30 tons, at the same expense and with 
the same effect as one locomotive engine drawing 90 tons. 
Hence arises what must appear an inconvenience and diffi- 
culty in applying these engines to one of the most profitable 
species of transport — the transport of passengers. It is im- 

* A contrivance might be applied in changes of level in railroads 
somewhat similar to locks in a canal. The train might be rolled upon a 
platform which might be raised by machinery ; and thus at the change of 
level there would be as it were steps from one level to another, up which 
the loads would be lifted by any power applied to work the machinery. 
The advantage in this case would be, that the trains might be adapted to 
work always upon a level. 



LOCOMOTIVE ENGINES ON RAILWAYS. 199 

practicable, even between places of the most considerable 
intercourse to obtain loads of passengers sufficiently great at 
each trip to maintain such an engine working on a railway.* 
The difficulty of collecting so considerable a number of per- 
sons, at any stated hour, to perform the journey, is obvious; 
and therefore, the only method of removing the inconveni- 
ence is to cause the same engine which transports passen- 
gers also to transport goods, so that the goods may make 
up the requisite supplement to the load of passengers. In 
this way, provided the traffic in goods be sufficient, such 
engines may start with their full complement of load, what- 
ever be the number of passengers. 

(98.) In comparing the extent of capital, and the annual 
expenditure of the Liverpool and Manchester line, and 
adopting it as a modulus in estimating the expenses of simi- 
lar undertakings projected elsewhere, there are several cir- 
cumstances to which it is important to attend. I have 
already observed on the large waste of capital in the item of 
locomtive engines which ought to be regarded as little more 
than experimental machines, leading to a rapid succession of 
improvements. Most of these engines are still in good 
working order, but have been abandoned for the reasons 
already assigned. Other companies will, of course, profit by 
the experience which has been thus purchased at a high price 
by the Liverpool Company. This advantage in favour of 
future companies will go on increasing until such companies 
have their works completed. 

A large portion of the current expense of a line of rail- 
way is independent of its length ; and is little less for the 
line connecting Liverpool and Manchester, than it would 



* On the occasion of races held at Newton, a place about 15 miles 
from Liverpool, two engines were sent, with trains of carriages, to take 
back to Liverpool the visiters to the races. Some accident prevented 
one of the engines from working on the occasion, and both trains were 
attached to the same engine: 800 persons were on this occasion drawn 
by the single engine to Liverpool in the space of about an hour. 



200 THE STEAM ENGINE. 

be for a line connecting Birmingham with Liverpool or 
London. 

The establishments of resident engineers, coach and wagon 
yards, &c. at the extremities of the line, would be little in- 
creased by a very great increase in the length of the railway; 
and the same observation will apply to other heads of expen- 
diture. 

It has been the practice of the canal companies between 
Liverpool and Manchester to warehouse the goods trans- 
ported between these towns, without any additional charge 
beyond the price of transport. The Railway Company, in 
competing with the canals, were, of course, obliged to offer 
like advantages: this compelled them to invest a considera- 
ble amount of capital in the building of extensive ware- 
houses, and to incur the annual expense of porterage, sala- 
ries, &c. connected with the maintenance of such storage. 
In a longer line of railway such expenses (if necessary at all) 
would not be proportionally increased. 

(99.) The comparison of steam-transport with the trans- 
port by horses, even when working on a railway, exhibits 
the advantage of this new power in a most striking point of 
view. To comprehend these advantages fully, it will be ne- 
cessary to consider the manner in which animal power is 
expended as a means of transport. The portion of the 
strength of a horse available for the purpose of a load depends 
on the speed of a horse's motion. To this speed there is 
a certain limit, at which the whole power of the horse will 
be necessary to move his own body, and at which, therefore, 
he is incapable of carrying any load ; and, on the other hand, 
there is a certain load which the horse is barely able to sup- 
port, but incapable of moving with any useful speed. Be- 
tween these two limits there is a certain rate of motion at 
which the useful effect of the animal is greatest. In horses 
of the heavier class, this rate of motion may be taken on the 
average as that of 2 miles an hour; and in the lighter de- 
scription of horses, 2£ miles an hour. Beyond this speed, 



LOCOMOTIVE ENGINES ON RAILWAYS. 201 

the load which they are capable of transporting diminishes 
in a very rapid ratio as the speed increases : thus, if 121 ex- 
press the load which a horse is able to transport a given dis- 
tance in a day, working at the rate of four miles an hour, 
the same horse will not be able to transport more than the 
load expressed by 64, the same distance, at 7 miles an hour; 
and, at 10 miles an hour, the load which he can transport 
will be reduced to 25. The most advantageous speed at 
which a horse can work being 2 miles an hour, it is found 
that, at this rate, working for 10 hours daily, he can trans- 
port 12 tons, on a level railway, a distance of 20 miles; so 
that the whole effect of a day's work may be expressed by 
240 tons carried 1 mile. 

But this rate of transport is inapplicable to the purposes 
of travelling; and therefore it becomes necessary, when 
horses are the moving power, to have carriages for passen- 
gers distinct from those intended for the conveyance of 
goods; so that the goods may be conveyed at that rate of speed 
at which the whole effect of the horse will be the greatest 
possible; while the passengers are conveyed at that speed 
which, whatever the cost, is indispensably necessary. The 
weight of an ordinary mail-coach is about two tons; and, on 
a tolerably level turnpike road, it travels at the rate of 10 
miles an hour. At this rate, the number of horses neces- 
sary to keep it constantly at work, including the spare horses 
indispensably necessary to be kept at the several stages, is 
computed at the rate of a horse per mile. Assuming the 
distance between London and Birmingham at. 100 miles, a 
mail-coach running between these two places would require 
100 horses; making the journey to and from Birmingham 
daily. The performance, therefore, of a horse working at 
this rate may be estimated at 2 tons carried 2 miles per day, 
or 4 tons carried 1 mile in a day. The force of traction on 
a good turnpike road is at least 20 times its amount on a 
level railroad. It therefore follows, that the performance 
of a horse on a railroad will be 20 times the amount of its 

26 



202 THE STEAM ENGINE. 

performance on a common road under similar circumstances. 
We may, therefore, take the performance of a horse work- 
ing at 10 miles an hour, on a level railroad, at 80 tons con- 
veyed 1 mile daily. 

The best locomotive engines used on the Liverpool rail- 
way are capable of transporting 150 tons on a level railroad 
at the same rate; and, allowing the same time for stoppage, 
its work per day would be 150 tons conveyed 200 miles, or 
30,000 tons conveyed 1 mile ; from which it follows, that 
the performance of one locomotive engine of this kind is 
equivalent to that of 7500 horses working on a good turn- 
pike road, or to 375 horses working on a railway. The con- 
sumption of fuel requisite for this performance, with the 
most improved engines used at present on the Manchester 
and Liverpool line, would be at the rate of eight* ounces of 
coke per ton per mile, including the waste of fuel incurred 
by the stoppages. Thus the daily consumption of fuel, un- 
der such circumstances, would amount to 15000 lbs. of coke ; 
and 2 lbs. of coke daily would perform the work of one 
horse on a good turnpike road; and 40 lbs. of coke daily 
would perform the work of one horse on a railway. 

In this comparison, the engine is taken at its most advan- 
tageous speed, while horse-power is taken at its least advan- 
tageous speed, if regard be only had to the total quantity of 
weight transported to a given distance. But, in the case 
above alluded to, speed is an indispensable element ; and 
steam, therefore, possesses this great advantage over horse 
power, that its most advantageous speed is that which is 
at once adapted to all the purposes of transport, whether 
of passengers or of goods. 

(100.) The effects of steam compared with horse-power, 
at lower rates of motion, will exhibit the advantages of the for- 
mer, though in a less striking degree. An eight-horse wa- 

• In an experimental trip with a heavy train at 12 miles an hour, I 
found the consumption of coke to be only four ounces per ton per hour. 
I believe, however, the practical consumption in ordinary work to be 
very nearly eight ounces. 



LOCOMOTIVE ENGINES ON RAILWAYS* 203 

gon commonly weighs 8 tons, and travels at the rate of 2$ 
miles an hour. Strong horses working in this way can tra- 
vel S hours daily ; thus each horse performs 20 miles a day. 
The performance, therefore, of each horse may be taken as 
equivalent to 20 tons transported 1 mile ; and his perform- 
ance on a railway being 20 times this amount, may be taken 
as equivalent to 400 tons transported 1 mile a day. The 
performance of a horse working in this manner is, therefore, 
5 times the performance of a horse working at 10 miles an" 
hour ; the latter effecting only the performance of 4 tons 
transported 1 mile per day on a good turnpike road, or 80 
tons on a railway. We shall hence obtain the proportion of 
the performance of horses working in wagons to that of a lo- 
comotive steam engine. Since 2 lbs. of coke are equivalent 
to the daily performance of a horse in a mail-coach, and 
40 lbs. on a railway, at 10 miles an hour, it follows that 10 
lbs. will be equivalent to the performance of a horse on a 
turnpike road, and 200 lbs. on a railway, at 2i miles an hour. 
Since a locomotive engine can perform the daily work of 
7500 mail-coach horses, it follows that it performs the work 
of 1500 wagon horses. 

These results must be understood to be subject to modifi- 
cations in particular cases, and to be only average calculations. 
Different steam-engines, as well as different horses, varying 
in their performance to a considerable extent ; and the roads 
on which horses work being in different states of perfection, 
and subject to different declivities, the performance must 
vary accordingly. 

In the practical comparison, also, of the results of so pow- 
erful an agent as steam applied on railways, with so slight a 
power as that of horses on common roads, it must be consi- 
dered that the great subdivision of load, and frequent times 
of starting, operate in favour of the performance of horses; 
inasmuch as it would oft.ener occur that engines capable of 
transporting enormous weights would start with loads infe- 
rior to their power, than would happen in the application of 
horse-power, where small loads may start at short intervals. 



204 THE STEAM ENGINE. 

This, in fact, constitutes a practical difficulty in the applica- 
tion of steam engines on railroads ; and will, perhaps, for 
the present, limit their application to lines connecting places 
of great intercourse. 

The most striking effect of steam power, applied on a rail- 
road, is the extreme speed of transport which is attained by 
it ; and it is the more remarkable, as this advantage never 
was foreseen before experience proved it. When the Liver- 
pool and Manchester line was projected, the transport of 
heavy goods was the object chiefly contemplated ; and al- 
though an intercourse in passengers was expected, it was not 
foreseen that this would be the greatest source of revenue to 
the proprietors. The calculations of future projectors will, 
therefore, be materially altered, and a great intercourse in 
passengers will be regarded as a necessary condition for the 
prosperity of such an undertaking. 

If this advantage of speed be taken into account, horse- 
power can scarcely admit of any comparison whatever with 
steam-power on a railway. In the experiments which I have 
already detailed, it appears that a steam engine is capable of 
drawing 90 tons at the rate of about 20 miles an hour, and 
that it could transport that weight twice between Liverpool 
and Manchester in about 3 hours. Two hundred and seventy 
horses working in wagons would be necessary to transport 
the same load the same distance in a day. It may be ob- 
jected, that this was an experiment performed under favour- 
able circumstances, and that assistance was obtained at the 
difficult point of the inclined plane. In the ordinary per- 
formance, however, of the engines drawing merchandise, 
where great speed is not attempted, the rate of motion is not 
less than 15 miles an hour. In the traihs which draw pas- 
sengers, the chief difficulty of maintaining a great speed 
arises from the stoppages on the road to take up and let 
down passengers. There are two classes of carriages at pre- 
sent used : the first class stops but once, at a point halfway 
between Liverpool and Manchester, for the space of a few 



LOCOMOTIVE ENGINES ON RAILWAYS. 205 

minutes. This class performs the thirty miles in an hour 
and a half, and sometimes in 1 hour and 10 minutes. On 
the level part of the road its common rate of motion is 27 
miles an hour ; and I have occasionally marked its rate, and 
found it above 30 miles ah hour. 

But these, which are velocities obtained in the regular 
working of the engines for the transport of passengers and 
goods, are considerably inferior to the power of the present 
locomotives with respect to speed. I have made some ex- 
perimental trips, in which more limited loads were placed 
upon the engines, by which I have ascertained that very con- 
siderably increased rates of motion are quite practicable. In 
one experiment I placed a carriage containing 36 persons 
upon an engine, with which I succeeded in obtaining the ve- 
locity of about 4S miles an hour, and I believe that an en- 
gine loaded only with its own tender has moved over 15 
miles in 15 minutes. 

It will then perhaps be asked, if the engines possess these 
great capabilities of speed, why they have not been brought 
into practical operation on the railroad, where, on the other 
hand, the average speed when actually in motion, does not 
exceed -25 miles an hour? In answer to this it may be 
stated, that the distance of 30 miles between Liverpool and 
Manchester is performed in an hour and a half, and that 10 
trains of passengers pass daily between these places : the 
mail, also, is transmitted three times a day between them. 
It is obvious that any greater speed than this, in so short a 
distance, would be quite needless. When, however, more 
extended lines of road shall be completed, the circumstances 
will be otherwise, and the despatch of mails especially will 
demand attention. Full trains of passengers, commonly 
transported upon the Manchester railroad, weigh about 50 
tons gross : with a lighter load, a lighter and more expedi- 
tious engine might be used. The expense of transport with 
such an engine would of course be increased ; but for this 
the increased expedition there would be ample compensation. 



206 THE STEAM ENGINE. 

When, therefore, London shall have heen connected with 
Liverpool, by a line of railroad through Birmingham, the 
commercial interest of these places will naturally direct at- 
tention to the greatest possible expedition of intercommuni- 
cation. For the transmission of mails, doubtless, peculiar 
engines will be built, adapted to lighter loads and greater 
speed. With such engines, the mails, with a limited num- 
ber of passengers, will be despatched ; and, apart from any 
possible improvement which the engines may hereafter re- 
ceive, and looking only at their present capabilities, I can- 
not hesitate to express my conviction that such a load may 
be transported at the rate of above 60 miles an hour. If we 
may indulge in expectations of what the probable improve- 
ments of locomotive steam engines may effect, I do not think 
that even double that speed is beyond the limits of mechani- 
cal probability. On the completion of the line of road from 
the metropolis to Liverpool we may, therefore, expect to 
witness the transport of mails and passengers in the short 
space of three hours. There will probably be about three 
posts a day between these and intermediate places. 

The great extension which the application of steam to the 
purpose of inland transport is about to receive from the 
numerous railroads which are already in progress, and from 
a still greater number of others which are hourly projected, 
impart to these subjects of inquiry considerable interest. 
Neither the wisdom of the philosopher, nor the skill of the 
statistician, nor the foresight of the statesman is sufficient to 
determine the important consequences by which the realiza- 
tion of these schemes must affect the progress of the human 
race. How much the spread of civilization, the diffusion of 
knowledge, the cultivation of taste, and the refinement of 
habits and manners depend upon the easy and rapid inter- 
mixture of the constituent elements of society, it is needless 
to point out. Whilst population exists in detached and in- 
dependent masses, incapable Of transfusion amongst each 
other, their dormant affinities are never called into action, 



LOCOMOTIVE ENGINES ON RAILWAYS. 207 

and the most precious qualities of each are never imparted 
to the other. Like solids in physics, they are slow to form 
combinations; but when the quality of fluidity has been im- 
parted to them, when their constituent atoms are loosened 
by fusion, and the particles of each flow freely through and 
among those of the other, then the affinities are awakened, 
new combinations are formed, a mutual interchange of quali- 
ties takes place, and compounds of value far exceeding those 
of the original elements are produced. Extreme facility of 
intercourse is the fluidity and fusion of the social masses, 
from whence such an activity of the affinities results, and 
from whence such an inestimable interchange of precious 
qualities must follow. We have, accordingly, observed, that 
the advancement in civilization and the promotion of inter- 
course between distant masses of people have ever gone on 
with contemporaneous progress, each appearing occasionally 
to be the cause or the consequence of the other. Hence it 
is that the urban population is ever in advance of the rural 
in its intellectual character. But, without sacrificing the 
peculiar advantages of either, the benefits of intercourse may 
be extended to both, by the extraordinary facilities which 
must be the consequence of the locomotive projects now in 
progress. By the great line of railroad which is in progress 
from London to Birmingham, the time and expense of 
passing between these places will, probably be halved, and 
the quantity of intercourse at least quadrupled, if we con- 
sider only the direct transit between the terminal points of 
the line; but if the innumerable tributary streams which will 
flow from every adjacent point be considered, we have no 
analogies on which to build a calculation of the enormous 
increase of intercommunication which must ensue. 

Perishable vegetable productions necessary for the wants 
of towns must at present be raised in their immediate 
suburbs; these, however, where they can be transported 
with a perfectly smooth motion at the rate of twenty miles 
an hour, will be supplied by the agricultural labourer of 



208 THE STEAM ENGINE. 

more distant points. The population engaged in towns, no 
longer limited to their narrow streets, and piled story over 
story in confined habitations, will be free to reside at dis- 
tances which would now place them far beyond reach of 
their daily occupations. The salubrity of cities and towns 
will thus be increased by spreading the population over a 
larger extent of surface, without incurring the inconvenience 
of distance. Thus the advantages of the country will be 
conferred upon the town, and the refinement and civilization 
of the town will spread their benefits among the rural popu- 
lation.* 

(101.) The quantity of canal property in these countries 
gives considerable interest to every inquiry which has for 
its object the relative advantage of this mode of transport, 
compared with that of railways, whether worked by horses 
or by steam-power; and this interest has been greatly in- 
creased by the recent extension of railway projects. This 
is a subject which I shall have occasion, in another work, to 
examine in all its details; and, therefore, in this place I shall 
advert to it but very briefly. 

When a floating body is moved on a liquid, it will suffer 
a resistance, which will depend partly upon the transverse 
section of the part immersed, and partly on the speed with 
which it is moved. It is evident that the quantity of the 
liquid which it must drive before it will depend upon that 
transverse section, and the velocity with which it will impel 
the liquid will depend upon its own speed. Now, so long 
as the depth of its immersion remains the same, it is demon- 
strable that the resistance will increase in proportion to the 
square of the speed; that is, with a double velocity there 
will be a fourfold resistance, with a triple velocity a ninefold 
resistance, and so on. Again, if the part immersed should 
be increased or diminished by any cause, the resistance, on 

* Some of the preceding observations appeared in an article contri- 
buted by me to the British and Foreign Review. 



LOCOMOTIVE ENGINES ON RAILWAYS. 209 

that account alone, will be increased or diminished in the 
same proportion. 

From these circumstances it will be apparent that a vessel 
floating on water, if moved with a certain speed, will require 
four times the impelling force to carry it forward with double 
the speed, unless the depth of its immersion be diminished 
as its speed is increased. 

Some experiments which have been made upon canals 
with boats of a peculiar construction, drawn by horses, have 
led to the unexpected conclusion, that, after a certain speed 
has been attained, the resistance, instead of being increased, 
has been diminished. This fact is not at variance with the 
law of resistance already explained. The cause of the phe- 
nomenon is found in the fact, that when the velocity has at- 
tained a certain point, the boat gradually rises out of the 
water; so that, in fact, the immersed part is diminished. 
The two conditions, therefore, which determine the resist- 
ance, thus modify each other : while the resistance is, on the 
one hand, increased in proportion to the square of the speed, 
it is, on the other hand, diminished in proportion to the di- 
minution of the transverse section of the immersed part of 
the vessel. It would appear that, at a certain velocity, these 
two effects neutralise each other ; and, probably, at higher 
velocities the immersed part may be so much diminished as 
to diminish the resistance in a greater degree than it is in- 
creased by the speed, and thus actually to diminish the 
power of traction. 

It is known that boats are worked on some of the Scottish 
canals, and also on the canal which connects Kendal with 
Preston, by which passengers are transported, at the rate of 
about ten miles an hour, exclusive of the stoppages at the 
locks, &c. , The power of horses, exerted in this way, is, of 
course, exerted more economically than they could be work- 
ed at the same speed on common roads ; and, probably, it is 
as economical as they would be worked by railroad. It is, 
probably, more economical than the transport of passengers 

27 



210 THE STEAM ENGINE. 

by steam upon railroads ; but the speed is considerably less, 
nor, from the nature of the impelling power, is it possible 
that it can be increased. 

There is reason to suppose that a like effect takes place 
with steam vessels. Upon increasing the power of the en- 
gines in some of the Post Office steam packets, it has been 
found, that, while the time of performing the same voyage 
is diminished, the consumption of fuel is also diminished. 
Now, since the consumption of fuel is in the direct ratio of 
the. moving power, and the latter in the direct ratio of the 
resistance, it follows that the resistance must in this case be 
likewise diminished. 

(102.) When a very slow rate of travelling is considered, 
-the useful effects of horse-power applied on canals is some- 
what greater than the effect of the same power applied on 
canals is somewhat greater than the effect of the same power 
applied on railways ; but at all speeds above three miles an 
hour, the effect on railways is greater; and when the speed 
is considerable, the canal becomes wholly inapplicable, while 
the railway loses none of its advantages. At three miles an 
hour, the performance of a horse on a canal and a railway is 
in the proportion of four to three to the advantage of the 
canal ; but at four miles an hour his performance on a rail- 
way has the advantage in very nearly the same proportion. 
At six miles an hour, a horse will perform three times more 
work on a railway than on a canal. At eight miles an hour, 
he will perform nearly five times more work. 

But the circumstance which, so far as respects passengers, 
must give railways, as compared with canals, an advantage 
which cannot be considered as less than fatal to the latter, is' 
the fact, that the great speed and cheapness of transit attain- 
able upon a railway by the aid of steam-power will always 
secure to such lines not only a monopoly of the travelling, 
but will increase the actual amount of that source of profit in 
an enormous proportion, as has been already made manifest 
between Liverpool and Manchester. Before the opening of 



LOCOMOTIVE ENGINES ON RAILWAYS. 211 

the railway there were about twenty-five coaches daily run- 
ning between Liverpool and Manchester. If we assume 
these coaches on the average to take ten persons at each trip, 
it will follow that the number of persons passing daily be- 
tween these towns was about 500. Let us, then, assume 
that 3000 persons passed weekly. This gives in six months 
7S,000. In the six months which terminated on the 31st of 
December 1S31, the number of passengers between the same 
towns, exclusive of any taken up on the road, was 256,3.21; 
and if some allowance be made for those taken up on the 
road, the number may be fairly stated at 300,000. At pre- 
sent there is but one coach on the road between Liverpool 
and Manchester; and it follows, therefore, that, besides tak- 
ing the monopoly of the transit in travellers, the actual 
number has been already increased in a fourfold proportion. 
The monopoly of the transit of passengers thus secured to 
the line of communication by railroad will always yield so 
large a profit as to enable merchandise to be carried at a 
comparatively low rate. 

In light goods, which require despatch, it is obvious that 
the railroad will always command the preference; and the 
question between that mode of communication and canals is 
circumscribed to the transit of those classes of heavy goods 
in which even a small saving in the cost of transport is a 
greater object than despatch. 

(103.) The first effect which the Liverpool railroad pro- 
duced on the Liverpool and Manchester canals was a fall in 
the price of transport ; and at this time, I believe, the cost 
of transport per ton on the railroads and on the canals is the 
same. It will, therefore, be naturally asked, this being the 
ease, why the greater speed and certainty of the railroad 
does not in every instance give it the preference, and alto- 
gether deprive the canals of transport ? This effect, how- 
ever, is prevented by several local and accidental causes, as 
well as by direct influence and individual interest. A large 
portion of the commercial and manufacturing population of 



212 THE STEAM ENGINE. 

Liverpool and Manchester have property invested in the 
canals, and are deeply interested to sustain them in opposi- 
tion to the railway. Such persons will give the preference 
to the canals in their own business, and will induce those 
over whom they have influence to do so in every case where 
speed of transport is not absolutely indispensable. 

Besides these circumstances, the canal communicates im- 
mediately with the shipping at Liverpool, and it ramifies in 
various directions through Manchester, washing the walls of 
many of the warehouses and factories for which the goods 
transported are destined. The merchandise is thus trans- 
ferred from the shipping to the boat, and brought directly to 
the door of its owner, or vice versa. If transported by the 
railway, on the other hand, it must be carried to the station 
at one extremity; and, when transported to the station at 
the other, it has still to be carried to its destination in differ- 
ent parts of the town. 

;,. These circumstances will sufficiently explain why the ca- 
nals still retain, and may probably continue to retain, a share 
of the traffic between these great marts. 



213 



CHAPTER XI. 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 

Railways and Turnpike Roads compared. — Mr. Gurney's inventions. — 
His Locomotive Steam Engine. — Its performances. — Predjudices and 
errors. — Committee of the House of Commons. — Convenience and safe- 
ty of Steam Carriages. — Hancock's Steam Carriage. — Mr. N. Ogle. — 
Trevithick's invention. — Proceedings against Steam Carriages. — Turn- 
pike Bills. — Steam Carriage between Gloucester and Cheltenham. — 
Its discontinuance. — Report of the Committee of the Commons. — Pre- 
sent State and Prospects of Steam Carriages. 

(104.) We have hitherto confined our observations to 
steam-power as a means of transport applied on railways, 
but modern speculation has not stopped here. Several at- 
temps have been made, and some of them attended with 
considerable success, to work steam-carriages on turnpike 
roads. The practicability of this project has been hitherto 
generally considered to be very questionable ; but if we car- 
ry back our view to the various epochs in the history of the 
invention of the steam engine, we shall find the same doubt, 
and the same difficulty, started at almost every important 
step in its progress. In comparing the effect of a turnpike 
road with that of a railway, there are two circumstances 
which obviously give facility and advantage to the railway. 
One is, that the obstructions to the rolling motion of the 
wheels, produced by the inequalities of the surface, are very 
considerably less on a railway than on a road ; less in the 
proportion of at least 1 to 20. This proportion, however, 
must depend much on the nature of the road with which the 
railway is compared. It is obvious that a well constructed 
road will offer less resistance than one ill constructed ; and 
it is ascertained that the resistance of a Macadamised road is 
considerably more than that of a road well paved with stones : 
the decision of this question, therefore, must involve the con- 



214 THE STEAM ENGINE. 

sideralion of another, viz. whether roads may not be con- 
structed by pavement or otherwise, smoother and better 
adapted to carriages moved in the manner of steam-carriages 
than the roads now used for horse power ? 

But besides the greater smoothness of rail-roads compared 
with turnpike roads, they have another advantage, which we 
suspect to have been considerably exaggerated by those who 
have opposed the project for steam-carriages on turnpike 
roads. One of the laws of adhesion, long since developed by 
experiment, and known to scientific men, is, that it is great- 
er between the surfaces of bodies of the same nature than be- 
tween those of a different nature. Thus between two metals 
of the same kind it is greater than between two metals of 
different kinds. Between two metals of any kind it is greater 
than between metal and stone, or between metal and wood. 
Hence, the wheels of steam-carriages running on a railroad 
have a greater adhesion with the road, and therefore offer a 
greater resistance to slip round without the advance of the 
carriage, than wheels would offer on a turnpike road ; for on 
a railroad the iron tire of the wheel rests in contact with the 
iron rail, while on a common road the iron tire rests in con- 
tact with the surface of stone, or whatever material the road 
may be composed of. Besides this, the dust and loose mat- 
ter which necessarily collect on a common road, when press- 
ed between the wheels and the solid base' of the road act 
somewhat in the manner of rollers, and give the wheels a 
greater facility to slip than if the road w T ere swept clean, and 
the wheels rested in immediate contact with its hard surface. 
The truth of this observation is illustrated on the railroads 
themselves, where the adhesion is found to be diminished 
whenever the rails are covered with any extraneous matter, 
such as dust or moist clay. Although the adhesion of the 
wheels of a carriage with a common road, however, be less 
than those of the wheels of a steam-carriage with a railroad, 
yet still the actual adhesion on turnpike roads is greater in 
amount than has been generally supposed, and is quite suffi- 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 215 

cient to propel carriages dragging after them loads of large 
amount. 

The relative facility with which carriages are propelled on 
railroads and turnpike roads equally affects any moving power, 
whether that of horses or steam engines ; and whether loads 
be propelled by the one power or the other, the railroad, as 
compared with the turnpike road, will always possess the 
same proportionate advantage ; and a given amount of power, 
whether of the one kind or the other, will always perform a 
quantity of work less in the same proportion on a turnpike 
road than on a railroad. But, on the other hand, the ex- 
pense of original construction, and of maintaining the repairs 
of a railroad, is to be placed against the certain facility which 
it offers to draught. 

In the attempts which have been made to adapt locomotive 
engines to turnpike roads, the projectors have aimed at the 
accomplishment of two objects: first, the construction of 
lighter and smaller engines; and, secondly, increased power. 
These ends, it is plain, can only be attained, with our present 
knowledge, by the production of steam of very high tem- 
perature and pressure, so that the smallest volume of steam 
shall produce the greatest possible mechanical effect. The 
methods of propelling the carriage have been in general simi- 
lar to that used in the railroad engines, yiz. either by cranks 
placed on the axles, the wheels being 'fixed upon the same 
axles, or by connecting the piston-rods with the spokes of 
the wheels, as in the engine represented in fig. 55. In some 
carriages, the boiler and moving power, and the bod}>- of the 
carriage which bears the passengers, are placed on the same 
wheels. In others, the engine is placed on a separate car- 
riage, and draws after it the carriage which transports the 
passengers, as is always the case on railways. 

The chief difference between the steam engines used on 
railways, and those adapted to propel carriages on turnpike 
roads, is in the structure of the boiler. In the latter it is 
essential that, while the power remains undiminished, the 



216 THE STEAM ENGINE. 

boiler should be lighter and smaller. The accomplishment 
of this has been attempted by various contrivances for so 
distributing the water, as to expose a considerable quantity 
of surface in contact with it to the action of the fire; spread- 
ing it in thin layers on flat plates; inserting it between plates 
of iron placed at a small distance asunder, the fire being ad- 
mitted between the intermediate plates; dividing it into 
small tubes, round which the fire has play; introducing it 
between the surfaces of cylinders placed one within another, 
the fire being admitted between the alternate cylinders, — 
have all been resorted to by different projectors. 

(105.) First and most prominent in the history of the ap- 
plication of steam to the propelling of carriages on turnpike 
roads, stands the name of Mr. Goldsworthy Gurney, a 
medical gentleman and scientific chemist, of Cornwall. In 
1822, Mr. Gurney succeeded Dr. Thompson as lecturer on 
chemistry at the Surrey Institution; and, in consequence of 
the results of some experiments on heat, his attention was 
directed to the project of working steam carriages on com- 
mon roads ; and since 1825 he has devoted his exertions in 
perfecting a steam engine capable of attaining the end he had 
in view. Numerous other projectors, as might have been 
expected, have followed in his wake. Whether they, or 
any of them, by better fortune, greater public support, or 
more powerful genius, may outstrip him in the career on 
which he has ventured,it would not, perhaps, at present, be 
easy to predict. But whatever be the event, to Mr. Gur- 
ney is due, and will be paid, the honour of first proving the 
practicability of the project; and in the history of the adap- 
tation of the locomotive engine to common roads, his name 
w r i!l stand before all others in point of time, and the success 
of his attempts will be recorded as the origin and cause of 
the success of others in the same race. 

The incredulity, opposition, and even ridicule, with which 
the project of Mr. Gurney was met, are very remarkable. 
His views were from the first opposed by engineers, without 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 217 

one exception. The contracted habit of mind, sometimes 
produced by an education. chiefly, if not exclusively, direct- 
ed to a merely practical object, subsequently confirmed by 
exclusively practical pursuits, may, perhaps, in some degree, 
account for this. But, I confess, it has not been without 
surprise that I have observed, during the last ten years, the 
utter incredulity which has prevailed among men of general 
science on this subject, — an incredulity which the most un- 
equivocal practical proof has scarcely yet dispelled. "Among 
scientific men," says Mr. Gurney, "my opinion had not a 
single supporter, with the exception of the late Dr. Wol- 
laston." 

The mistake which so long prevailed in the application of 
locomotives on railroads, and which, as we have shown, 
materially retarded the progress of that invention, was 
shared by Mr. Gurney. Without reducing the question to 
the test of experiment, he took for granted, in his first at- 
tempts, that the adhesion of the wheels with the road was 
too slight to propel the carriage. He was assured, he says, 
by eminent engineers, that this was a point settled by actual 
experiment. It is strange, however, that a person of his 
quickness and sagacity did not inquire after the particulars 
of these " actual experiments." So, however, it was ; and, 
taking for granted the inability of the wheels to propel, he 
wasted much labour and skill in the contrivance of levers 
and propellers, which acted on the ground in a manner 
somewhat resembling the feet of horses, to drive the car- 
riage forward. After various fruitless attempts of this kind, 
the experience acquired in the trials to which they gave 
rise at last forced the truth upon his notice, and he found that 
the adhesion of the wheels was not only sufficient to propel 
the carriage heavily laden on level roads, but was capable of 
causing it to ascend all the hills which occur on ordinary 
turnpike roads. In this manner it ascended all the hills 
■between London and Barnet, London and Slanmore, 

28 



218 THE STEAM ENGINE. 

Stanmore Hill, Brockley Hill, and mounted Old Highgate 
Hill, the last at one point rising one foot in nine. 

It would be foreign to my present object to detail minutely 
all the steps by which Mr. Gurney gradually improved his 
contrivance. This, like other inventions, has advanced by 
a series of partial failures; but it has at length attained that 
state, in which, by practice alone, on a more extensive 
scale, a 'further degree of perfection can be obtained. 

(106.) The boiler of this engine is so constructed that 
there is no part of it, not even excepting the grate bars, in 
which metal exposed to the action of the fire is out of con- 
tact with water. If it be considered how rapidly the action 
of an intense furnace destroys metal when water is not 
present to prevent the heat from accumulating, the advan- 
tage of this circumstance will be appreciated. I have seen 
the bars of a new grate, never before used, melted in a single 
trip between Liverpool and Manchester ; and the inventor 
of another form of locomotive engine has admitted to me 
that his grate bars, though of a considerable thickness, would 
not last more than a week. In the boiler of Mr. Gurney, 
the grate bars themselves are tubes filled with water, and 
form, in fact, a part of the boiler itself. This boiler consists 
of three strong metal cylinders placed in a horizontal posi- 
tion one above the other. A section, made by a perpendi- 
cular or vertical plane, is represented in fig. 62. The ends 
of the three cylinders, just mentioned, are represented at 
d, h, and i. In the side of the lowest cylinder d are inserted 
a row of tubes, a ground plan of which is represented in fig. 
63. These tubes, proceeding from the side of the lowest 
cylinder d, are inclined slightly upwards, for a reason which 
I shall presently explain. From the nature of the section, 
only one of these tubes is visible in fig. 62, at c. The other 
extremities of these tubes at a are connected with the same 
number of upright tubes, one of which is expressed at e. 
The upper extremities a of these upright tubes are connected 
with another set of tubes k, equal in number, proceeding 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 



219 



from g, inclining slightly upwards, and terminating in the 
second cylinder h. 

An end view of the boiler is exhibited in fig. 64., where 
the three cylinders are expressed by the same letters. Be- 




Fig. 63. 



a 



E 



t 



D > 



o 



r^- 



Z^Qa 






S= 



TT? 



OTa 






220 THE STEAM ENGINE. 

tween the cylinders d and h there are two tubes of communi- 
cation b, and two similar tubes between the cylinders h and i. 
From the nature of the section these appear only as a single 
tube in fig. 62. From the top of the cylinder i proceeds a 
tube n, by which steam is conducted to the engine. 
Fig. 64. 



It will be perceived that the space f is enclosed on every 
side by a grating of tubes, which have free communication 
with the cylinders d and h, which cylinders have also a free 
communication with each other by the tubes b. It follows, 
therefore, that if water be supplied to the cylinder i, it will 
descend through the tubes, and first filling the cylinder d 
and the tubes c, will gradually rise in the tubes b and e, 
will next fdl the tubes ic and the cylinder h. The gratino- 
of water pipes c e k forms the furnace, the pipes c being the 
fire-bars, and the pipes e and b being the back and roof of 
the stove. The fire-door, for the supply of fuel, appears at 
m, fig. 64. The flue issuing between the tubes f is conduct- 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 221 

ed over the tubes k, and the flame and hot air are carried 
off through a chimney. That portion of the heat of the 
burning fuel, which in other furnaces destroys the bars of 
the grate, is here expended in heating the water contained 
in the tubes c. The radiant heat of the fire acts upon the 
tubes k, forming the roof of the furnace, on the tube e at the 
back of it, and partially on the cylinders d and h, and the 
tubes b. The draft of hot air and flame passing into the 
flue at a, acts- upon the posterior surfaces of the tubes e, and 
the upper sides of the tubes k, and finally passes into the 
chimney. 

As the water in the tubes c e k is heated, it becomes spe- 
cifically lighter than water of a less temperature, and conse- 
quently acquires a tendency to ascend. It passes, therefore, 
rapidly into h. Meanwhile the colder portions descend, and 
the inclined positions of the tubes c and k give play to this 
tendency of the heated water, so that a prodigiously rapid 
circulation is produced, when the fire begins to act upon the 
tubes. When the water acquires such a temperature that 
steam is rapidly produced, steam bubbles are constantly 
formed in the tubes surrounding the fire; and if these re- 
mained stationary in the tubes, the action of the fire would 
not only decompose the steam, but render the tubes red hot, 
the water not passing through them to carry off the heat. 
.But the inclined position of the tubes, already noticed, ef- 
fectually prevents this injurious consequence. A steam bub- 
ble which is formed either in the tubes c or k, having a ten- 
dency to ascend proportional to its lightness as compared 
with water, necessarily rushes upwards; if in c towards a, 
and if in k towards h. But this motion of the steam is also 
aided by the rapid circulation of the water which is continu- 
ally maintained in the tubes, as already explained, otherwise 
it might be possible, notwithstanding the levity of steam 
compared with water, that a bubble might remain in a narrow 
tube without rising. I notice this more particularly, because 
the burning of the tubes is a defect which has been errone- 



222 THE STEAM ENGINE. 

ously, in my opinion, attributed to this boiler. To bring 
the matter to the test of experiment, I have connected two 
cylinders, such as d and h, by a system of glass tubes, such 
as represented at c e k. The rapid and constant circulation 
of the water was then made evident : bubbles of steam were 
formed in the tubes, it is true ; but they passed with great 
rapidity into the upper cylinder, and rose to the surface, so 
that the glass tubes never acquired a higher temperature than 
that of the water which passed through them. 

This I conceive to be the chief excellence of Mr. Gur- 
ney's boiler. It is impossible that any part of the metal of 
which it is formed can receive a greater temperature than 
that of the water which it contains ; and that temperature, 
as is obvious, can be regulated with the most perfect certain- 
ty and precision. I have seen the tubes of this boiler, while 
exposed to the action of the furnace, after that action has 
continued for a long period of time, and I have never observ- 
ed the soot which covers them to redden, as it would do if 
the tube attained a certain temperature. 

Every part of the boiler being cylindrical, it has the form 
which, mechanically considered, is most favourable to 
strength, and which, within given dimensions, contains the 
greatest quantity of water. It is also free from the defects 
arising from unequal expansion, which are found to be most 
injurious in tubular boilers. The tubes c and k can freely 
expand in the direction of their length, without being loos- 
ened at their joints, and without straining any part of the 
apparatus; the tubes, e, being short, are subject to a very 
slight degree of expansion ; and it is obvious that the long 
tubes, with which the} 7 are connected, will yield to this 
without suffering a strain, and without causing any part of 
the apparatus to be loosened. 

When water is converted into steam, any foreign matter 
which may be combined with it is disengaged, and is depo- 
sited on the bottom of the vessel in which the water is eva- 
porated. All boilers, therefore, require occasional cleans- 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 223 

ing, to prevent the crust thus formed from accumulating ; 
and this operation, for obvious reasons, is attended with pe- 
liar difficulty in tubular boilers. In the case before us, the 
the crust of deposited matter would gather and thicken in 
the tubes c and k, and if not removed, would at length 
choke them. But besides this, it would be attended with a 
still worse effect; for, being a bad conductor, it would inter- 
cept the heat in its transit from the fire tp the water and 
would cause the metal of the tube to become unduly heated. 
Mr. Gurney of course foresaw this inconvenience, and con- 
trived an ingenious chemical method of removing it by oc- 
sionally injecting through the tubes such an acid as would 
combine with the deposite, and carry it away. This method 
was perfectly effectual; and although its practical application 
was found to be attended with difficulty in the hands of com- 
mon workmen, Mr. Gurney was persuaded to adhere to it 
by the late Dr. Wollaston, until experience proved the im- 
possibility of getting it effectually performed, under the cir- 
cumstances in which boilers are commonly used. Mr. Gur- 
ney then adopted the more simple, but not less effectual, me- 
thod of removing the deposite by mechanical means. Oppo- 
site the mouths of the tubes, and on the other side of the cy- 
linders d and h, are placed a number of holes, which, -when 
the boiler is in use, are stopped by pieces of metal screwed 
into them. When the tubes require to be cleaned these stop- 
pers are removed, and an iron scraper is introduced through 
the holes into the tubes, which being passed backwards and 
forwards, removes the deposite. The boiler may be thus 
cleaned by a common labourer in half a day, at an expense 
of about Is. Qd. 

The frequency of the periods at which a boiler of this kind 
requires cleaning must depend, in a great degree, on the na- 
ture of the water which is used ; one in daily use with the 
water of the river Thames would not require cleaning more 
than once in a month. Mr. Gurney states that with water 



224 THE STEAM ENGINE. 

of the most unfavourable description, once a fortnight would 
be sufficient. 

(107.) In the more recent boilers constructed by- Mr. 
Gurney, he has maintained the draught through the furnace, 
by the method of projecting the waste steam into the chim- 
neys ; a method so perfectly effectual, that it is unlikely to 
be superseded by any other. The objection which has been 
urged against it in locomotive engines, working on turnpike 
roads, is, that the noise which it produces has a tendency to 
frighten horses. 

In the engines on the Liverpool road, the steam is allow- 
ed to pass directly from the eduction pipe of the cylinder to 
the chimney, and it there escapes in puffs corresponding with 
the alternate motion of the pistons, and produces a noise, 
which, although attended with no inconvenience on the rail- 
road, would certainly be objectionable on turnpike roads. 
In the engine used in Mr. Gurney's steam-carriage, -the 
steam which passes from the cylinders is conducted to.a re- 
ceptacle, which he calls a blowing box. This box serves the 
same purpose as the upper chamber of a smith's bellows. It 
receives the steam from the cylinders in alternate puffs, but 
lets it escape into the chimney in a continued stream by a 
number of small jets. Regular draught is by this means pro- 
duced, and no noise is perceived. Another exit for the steam 
is also provided, by which the conductor is enabled to in- 
crease or diminish, or to suspend altogether, the draught in 
the chimney, so as to adapt the intensity of the fire to the 
exigencies of the road. This is a great convenience in prac- 
tice •, because, on some roads, a draught is scarcely required, 
while on others a powerful blast is indispensable. 

Connected with this blowing box, is another ingenious ap- 
paratus of considerable practical importance. The pipe 
through which the water which feeds the boiler is conducted 
to it from the tank is carried through this blowing box, 
within which it is coiled in a spiral form, so that an exten- 
sive thread of the feeding water is exposed to the heat of the 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 225 

waste steam which has escaped from the cylinders, and 
which is enclosed in this blowing box. In passing through 
this pipe the feeding water is raised from the ordinary tem- 
perature of about 60° to the temperature of 212°. The fuel 
necessary to accomplish this is, therefore, saved, and the 
amount of this is calculated at l-6th of all that is necessary 
to evaporate the water. Thus, l-6th of the expense of fuel is 
saved. But, what is much more important in a locomotive 
engine, a portion of the weight of the engine is saved with- 
out any sacrilice of its power. There is still another great 
advantage attending this process. The feeding water in the 
worm just mentioned, while it takes up the heat from the 
surrounding steam in the blowing box, condenses l-6th of 
the waste steam, which is thence conducted to the tank, 
from which the feeding water is pumped, saving in this man- 
ner l-6th in weight and room of the water necessary to be 
carried in the carriage for feeding the boiler.* 

So far as the removal of all inconvenience arising from 
noise, this contrivance has been proved by experience to be" 
perfectly effectual, t 

In all boilers, the process of violent ebullition causes a 
state of agitation in the water, and a number of counter cur- 
rents, by which, as the steam is disengaged from the surface 
of the water, it takes with it a considerable quantity of wa- 
ter in mechanical mixture. If this be carried through the 
cylinders, since it possesses none of the qualities of steam, 
and adds nothing to the power of the vapour with which it 
is combined, it causes an extensive waste of heat and water, 

* In boilers constructed for stationary purposes, or for steam naviga- 
tion, the steam-pipe, after it has passed through the blowing box, is con- 
tinued and made to form a series of returned flues over the boiler, so as 
to take up the waste heat after it has passed the boiler, and before it 
reaches the chimney. But in locomotive engines for common roads, it 
has been found by experience, that the power gained by the waste heat 
is not sufficient to propel the weight of the material necessary for taking 
it up. 

f See Report of the Commons. 

29 



226 THE STEAM ENGINE. 

and produces other injurious effects. In every boiler there- 
fore, some means should be provided for the separation of 
the water thus suspended in the steam, before the steam is 
conducted to the cylinder. In ordinary plate boilers, the 
large space which remains above the surface of the water 
serves this purpose. The steam being there subject to no 
agitation or disturbance, the water mechanically suspended 
in it descends by its own gravity, and leaves pure steam in 
the upper part. In the small tubular boilers, this has been 
a matter, however, of greater difficulty. The contracted 
spaces in which the ebullition takes place, causes the water 
to be mixed with the steam in a greater quantity than could 
happen in common plate boilers : and the want of the same 
steam-room renders the separation of the water from the 
steam a matter of some difficulty. These inconveniences 
have been overcome by a succession of contrivances of great 
ingenuity. I have already described the rapid and regular 
circulation effected by the arrangement of the tubes. By 
this a regularity in the currents is established, which alone 
has a tendency to diminish the mixture of water with the 
steam. But in addition to this, a most effectual method of 
separation is provided in the vessel i, which is a strong, iron 
cylinder of some magnitude, placed out of the immediate in- 
fluence of the fire. A partial separation of the steam from 
the water takes place in the cylinder h ; and the steam with 
the water mechanically suspended in it, technically called 
moist steam, rises into the separator i. Here, being free 
from all agitation and currents, and being, in fact, quiescent, 
the particles of water fall to the bottom, while the pure 
steam remains at the top. This separator, therefore, serves 
all the purposes of the steam-room above the surface of the 
water in the large plate boilers. The dry steam is thus col- 
lected and ready for the supply of the engine through the 
tube n, while the water, which is disengaged from it, is col- 
lected at the bottom of the separator, and is conducted 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 227 

through the tube t to the lowest vessel d, to be again cir- 
culated through the boiler. 

The pistons of the engine work oh the axles of the hind 
wheels of the carriage which bears the engine, by cranks, as 
in the locomotives on the Manchester railway, so that the 
axle is kept in a constant state of rotation while the engine 
is at work. The wheels placed on this axle are not perma- 
nently fixed or keyed upon it, as in the Manchester loco- 
motives; but they are capable of turning upon it in the 
same manner as ordinary carriage wheels. Immediately 
within these wheels there are fixed upon the axles two pro- 
jecting spokes or levers, which revolve with the axle, and 
which take the position of two opposite spokes of the wheel. 
These may be occasionally attached to the wheel or detach- 
ed from it; so that they are capable of compelling the wheels 
to turn with the axle, or leaving the axle free to turn inde- 
pendent of the wheel, or the wheel independent of the axle, 
at the pleasure of the conductor. It is by these levers that 
the engine is made to propel either or both of the wheels. 
If both pairs of spokes are thrown into connexion with the 
wheels, the crank shaft or axle will cause both wheels to 
turn with it, and in that case the operation of the carriage is 
precisely the same as those of the locomotives already de- 
scribed upon the Liverpool and Manchester line; but this is 
rarely found to be necessary, since the adhesion of one wheel 
with the road is generally sufficient to propel the carriage, 
and consequently only one pair of these fixed levers are ge- 
nerally used, and the carriage propelled by only one of the 
two hind wheels. The fore wheels of the carriage turn 
upon a pivot similar to those of a four-wheeled coach. The 
position of the'se wheels is changed at pleasure by a simple 
pinion and circular rack, which is moved by the conductor, 
and in this manner the carriage is guided with precision and 
facility. 

The force of traction necessary to propel a carriage upon 
common roads must vary with the variable quality of the 



228 THE STEAM ENGINE. 

road, and consequently the propelling power, or the pressure 
upon the pistons of the engine, must be susceptible of a cor- 
responding variation ; but a still greater variation becomes 
necessary from the undulations and hills which are upon all 
ordinary roads. This necessary change in the intensity of 
the impelling power is obtained by restraining the steam in 
the boiler by the throttle valve, as already described in the 
locomotive engines on the rail-road. This principle, how- 
ever, is carried much further in thepresent case. The steam 
in the boiler may be at a pressure of from 100 to 200 lbs. 
on the square inch ; while the steam on the working piston 
may not exceed 30 or 40 lbs. on the inch. Thus an im- 
mense increase of power is always at the command of the 
conductor; so that when a hill is encountered, or a rough 
piece of road, he is enabled to lay on power sufficient to 
meet the exigency of the occasion. 

The two difficulties which have been always, apprehended 
in the practical working of steam carriages upon common 
roads are, first, the command of sufficient power for hills 
and rough pieces of road ; and, secondly, the apprehended 
insufficiency of the adhesion of the wheels with the road to 
propel the carriage. The former of these difficulties has 
been met by allowing steam of a very great pressure to be 
constantly maintained in the boiler with perfect safety. As 
to the second, all experiments tend to show that there is no 
ground for the supposition that the adhesion of the wheels 
is in any case insufficient for the purposes of propulsion. 
Mr. Gurney states, that he has succeeded in driving car- 
riages thus propelled up considerable hills on the turnpike 
roads about London. He made a journey to Barnet with 
only one wheel attached to the axle, which was found suffi- 
cient to propel the carriage up all the hills upon that road. 
The same carriage, with only one propelling wheel, also 
went to Bath, and surmounted all. the hills between Cranford 
Bridge and Bath, going and returning. 

A double stroke of the piston produces one revolution of 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 22!» 

the propelling wheels, and causes the carriage to move 
through a space equal to the circumference of those wheels. 
It will therefore be obvious, that the greater the diameter of 
the wheels, the better adapted the carriage is for speed; and, on 
the other hand, wheels of smaller diameter are better adapted 
for power. In fact, the propelling power of an engine on the 
wheels will be in the inverse proportion to their <liameter. 
In carriages designed to carry great weights at a moderate 
speed, smaller wheels will be used; while in those intended 
for the transport- of passengers at considerable velocities, 
wheels of at least 5 feet in diameter are most advantageous. 
Among the numerous popular prejudices to which this 
new invention has given rise, one of the most mischievous 
in its effects, and most glaring in its falsehood, is the notion 
that carriages thus propelled are more injurious to roads than 
carriages drawn by horses. This error has been most clearly 
and successfully exposed in the evidence taken before the 
committee of the House of Commons upon steam carriages. 
It is there fully demonstrated, not only that carriages thus 
propelled did not wear a turnpike road more rapidly than 
those drawn by horses, but that, on the other hand, the wear 
by the feet of horses is far more rapid and destructive than 
any which could be produced by the wheels of carriages. 
Steam carriages admit of having the tires of the wheels 
broad, so as to act upoirthe road more in the manner of rol- 
lers, and thereby to give consistency and firmness to the 
material of which the road is composed. The driving 
wheels, being fully proved not to slip upon the road, do not 
produce any effects more injurious than the ordinary rolling 
wheels ; consequently the wear occasioned by a steam car- 
riage upon a l'oad is not more than that produced by a car- 
riage drawn by horses of an equivalent weight and the same 
or equal tires; but the wear produced by the pounding and 
digging of horses' feet in draught is many times greater than 
that produced by the wear of any carriage. Those who still 
have doubts upon this subject, if there be any such persons, 



230 THE STEAM ENGINE. 

will be fully satisfied by referring to the evidence which ac- 
companies the report of the committee of the House of Com- 
mons, printed in October, 1S31. In that report they will 
not only find demonstrative evidence that the introduction 
of steam carriages will materially contribute to the saving in 
the wear of turnpike roads, but also that the practicability of 
working such carriages with a great saving to the public- — 
with great increase of speed and other conveniences to the 
traveller — is fully established. 

The weight of machinery necessary for steam carriages is 
sometimes urged as an objection to their practical utility. 
Mr. Gurney states, that, by successive improvements in 
the details of the machinery, the weight of his carriages, 
without losing any of the propelling power, may be reduced 
to 35 cwt., exclusive of the load and fuel and water: but 
thinks that it is possible to reduce the weight still further. 

A steam carriage constructed by Mr. Gurney, weighing 
35 cwt., working for 8 hours, is found, according to his 
statement, to do the work of about 30 horses. He calcu- 
lates that the weight of his propelling carriage, which would 
be capable of drawing 18 persons, would be equal to the 
weight of 4 horses; and the carriage in which these persons 
would be drawn would have the same weight as a common 
stage coach capable^of carrying the same number of persons. 
Thus the weight of the whole — the. propelling carriage and 
the carriage for passengers taken together — would be the 
same with the weight of a common stage coach, with 4 
horses inclusive. 

(108.) There are two methods of applying locomotives 
upon common roads to the transport of passengers or goods; 
the one is by causing the locomotive to carry, and the other 
to draw the load; and different projectors have adopted the 
one and the other method. Each is attended with its advan- 
tages and disadvantages. If the same carriage transport the 
engine and the load, the weight of the whole will be less in 



LOCOMOTIVE ENGINES ON TURNPIKE KOADS. 231 

proportion to the load carried ; also a greater pressure may 
be produced on the wheels by which the load is propelled. 
It is also thought that a greater facility in turning and gujd- 
ing the vehicle, greater safety in descending the hills, and a 
saving in the original cost, will be obtained. On the other 
hand, when the passengers are placed in the same carriage 
with the engine, they are necessarily more exposed to the 
noise of the machinery and to the heat of the boiler and fur- 
nace. The danger of explosion is so slight, that, perhaps, 
it scarcely deserves to be mentioned; but still the apprehen- 
sion of danger on the part of the passengers, even though 
groundless, should not be disregarded. This apprehension 
will be obviously removed or diminished by transferring the 
passengers into a carriage separate from the engine ; but the 
greatest advantage of keeping the engine separate from the 
passengers is the facility which it affords of changing one 
engine for another in case of accident or derangement on the 
road, in the same manner as horses are changed at the dif- 
ferent stages: or, if such an accident occur in a place where 
a new engine cannot be procured, the load of passengers may 
be carried forward by horses, until it is brought to some 
station where a locomotive may be obtained. There is also 
an advantage arising from the circumstance that when the 
engines are under repair, or in process of cleaning, the car- 
riages for passengers are not necessarily idle. Thus the 
same number of carriages for passengers will not be required 
when the engine is used to draw as when it is used to carry. 

In case of a very powerful engine being used to carry 
great loads, it would be quite impracticable to place the en- 
gine and loads on four wheels, the pressure being such as no 
turnpike road could bear. In this case it would be indispen- 
sably necessary to place a part of the load at least upon sepa- 
rate carriages to be drawn by the engine. 

In the comparison of carriages propelled by steam with 
carriages drawn by horses, there is no respect in which the ad- 
vantage of the former is so apparent as the safety afforded to 



232 THE STEAM ENGINE. 

the passenger. Steam power is under the most perfect control, 
and a carriage thus propelled is capable of being guided with 
the most admirable precision. It is also capable of being stop- 
ped almost suddenly, whatever be its speed : it is capable of 
being turned within a space considerably less than that which 
would be necessary for four-horse coaches. In turning sharp 
corners, there is no danger, with the most ordinary care on the 
part of the conductor. On the other hand, horse power, as is 
well known, is under very imperfect control, especially 
when horses are used, adapted to that speed which at pre- 
sent is generally considered necessary for the purpose of 
travelling. " The danger of being run away with and over- 
turned," says Mr. Farey, in his evidence before the House 
of Commons, " is greatly diminished in a steam coach. It 
is very difficult to control four such horses as can draw a 
heavy stage coach ten miles an hour, in case they are fright- 
ened or choose to run away ; and, for such quick travelling, 
they must be kept in that state of courage that they are al- 
ways inclined to run away, particularly down hill, and at 
sharp turns in the road. Steam power has very little cor- 
responding danger, being perfectly controllable, and capable 
of having its power reversed to retard in going down hill. 
It must be carelessness that would occasion the overturning 
of a steam carriage. . The chance of breaking down has been 
hitherto considerable, but it will not be more than in stage 
coaches when the work is truly proportioned and properly 
executed. The risk from explosion of the boiler is the only 
new cause of danger, and that I consider not equivalent to 
the danger from horses." 

That the risk of accident from explosion is very slight in- 
deed, if any such risk exists, may be proved from the fact 
that the boilers used on the Liverpool and Manchester rail- 
road being much larger, and, in proportion, inferior in 
strength to those of Mr. Gurney, and other steam carriage 
projectors, have never yet been productive of any injurious 
consequences by explosion, although they have frequently 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 233 

burst. I have stood close to a locomotive on the railroad 
when the boiler burst. The effect was that the water passed 
through the tubes into the fire and extinguished it, but no 
other consequence ensued. 

In fig. 65. is represented the appearance of a locomotive 
of Mr. Gicrney's drawing after it a carriage for passengers. 
Fig. 65. 




(109.) One of the greatest difficulties which locomotives 
upon a turnpike road have to encounter is the ascent of very 
steep hills, for it is agreed upon all hands that hills of very- 
moderate inclinations present no difficulty which may not 
be easily overcome, even in the present state of our know- 
ledge. The fact of Mr. Gurney having propelled his car- 
riage up Old Highgate Hill, when the apparatus was in a 
a much more imperfect state than that to which it has now 
attained, establishes the mere question of the possibility of 
overcoming the difficulty ; but it remains still to be decided 
whether the inconvenience caused by providing means of 
meeting the exigency of very steep hills may not be greater 
than the advantage of being able to surmount them can com- 
pensate for : and Mr. Farey, whose authority upon subjects 
of this kind is entitled to the highest respect, thinks that it 
is upon the whole more advantageous to provide, at very steep 
hills, post horses to assist the steam carriage up them, than to 
incur the inconvenience of providing the necessary power and 
strength of machinery for occasions which at best but rarely 
occur. If the question merely referred to the command of mo- 
tive power, it appears to me that Mr. Gurney J s boiler would 

30 



234 THE STEAM ENGINE. 

be amply sufficient to supply all that could be required for 
any hills which occur upon turnpike roads; but it is not to be 
forgotten, that not merely an ample supply of motive pow- 
er, but also a strength and weight in the machinery propor- 
tionate to the power to be exerted, is indispensably neces- 
sary. The strength and weight necessary to ascend a very 
steep hill will be considerably greater than that which is 
necessary for a level road, or for hills of moderate inclina- 
tions ; and it follows that if we ascend those steep hills by 
the unaided power of the locomotive, we must load the en- 
gine with all the weight of machinery requisite for such 
emergencies, such additional weight being altogether unne- 
cessary, and therefore a serious impediment upon all other 
parts of the road, inasmuch as it must exclude an equivalent 
weight of goods or passengers, which might otherwise be 
transported, and thereby in fact diminish proportionally the 
efficiency of the machine. It is right, however, to observe, 
that this is a point upon which a difference of opinion is en- 
tertained by persons equally competent to form a judgment, 
and that some consider that it is practicable to construct an 
engine without inconvenient weight which will ascend all 
the hills which occur upon turnpike roads. 

However this may be, the difficulty is one which the im- 
proved system of roads in England renders of a compara- 
tively trifling nature. If horses were resorted to as the 
means of assistance up such hills as the engine would be in- 
capable of surmounting, such aid would not be requisite 
more than twice or thrice upon the mail-coach road between 
London and Holyhead; and the same may be said of the 
roads connecting the greatest points of intercourse in the 
kingdom. Such. hills as the ascent at Pentonville upon 
the New Road, the ascent in St. James's Street, the ascent 
from Waterloo Place to the County Fire Office, the ascent 
at Highgate Archway, present no difficulty whatever. It is 
only Old Highgate Hill, and hills of a similar kind, which 
would ever require a supply of horses in aid of the engine. 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 



235 



I therefore incline to agree with Mr. Farcy, that, at least 
for the present, it will be more expedient to construct car- 
riages adapted to surmount moderate hills only, and to pro- 
vide post horses in aid of the extreme emergencies to which 
I have just alluded. 

(110.) In the boiler to be used in the steam carriage pro- 
jected by Mr. Walter Hancock, the subdivision of the water 
is accomplished by dividing a case or box by a number of 
thin plates of metal like a galvanic battery, the water being 
allowed to flow between every alternate pair of plates, at e, 
fig. 66., and the intermediate spaces h forming the flue 
through which the flame and hot air are propelled. 

In fact, a number of thin plates of water are. exposed on 
both sides to the most intense action of flame artd heated air; 
so that steam of % a high pressure is produced in great abun- 
bance and with considerable rapidity. The plates forming 
the boiler are bolted together by strong iron ties, extending 
across the boiler, at right angles to the plates, as represented 

Fig. 66. 




236 THE STEAM ENGINE. 

in the figure. The distance between the plates is two 
inches. 

There are ten flat chambers of this kind for water, and in- 
termediately between them ten flues. Under the flues is 
the fire-place, or grate; containing six square feet of fuel in 
vivid combustion. The chambers are all filled to about two 
thirds of their depth with water, and the other third is left 
for steam. The water-chambers, throughout the whole 
series, communicate with each other both at top and bottom, 
and are held together by two large bolts. By releasing these 
bolts, at any time, the chambers fall asunder; and by screw- 
ing them up they may be all made tight again. The water 
is supplied to the boiler by a forcing-pump, and the steam 
issues from the centre of one of the flues at the top. 

These boilers are constructed to bear a pressure of 400 or 
500 lbs. on the square inch; but the average pressure of the 
steam on the safety valve is from 60 to 100. There are 
100 square feet of surface in contact with the water exposed 
to the fire. The stages which such an engine performs are 
eight miles, at the end of which a fresh supply of fuel and 
water are taken in. • It requires about two bushels of coke 
for each stage. 

The steam carriage of Mr. Hancock differs from that of 
Mr. Gurney in this, — that in the former the passengers 
and engine are all placed on the same carriage. The boiler 
is placed behind the carriage; and there is an engine-house 
between the boiler and the passengers, who are placed on 
the fore part of the vehicle; so that all the machinery is be- 
hind them. The carriages are adapted to carry 14 passen- 
gers, and weigh, exclusive of their load, about 3§ tons, the 
tires of the wheels being about 3J inches in breadth. Mr. 
Hancock states, that the construction of his boiler is of such 
a nature, that, even in the case of bursting, no danger is to 
be apprehended, nor any other inconvenience than the 
stoppage of the carriage. He states that, while travelling 
about 9 miles an hour, and working with a pressure of about 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 237 

100 lbs. on the square inch, loaded with 13 passengers, the 
carriage was suddenly stopped. At first the cause of the 
accident was not apparent; but, on opening one of the cocks 
Of the boiler, it was found that it contained neither steam 
nor water. Further examination proved that the boiler had 
burst. On unscrewing the bolts, it was found there were 
several large holes in the plates of the water-chamber, 
through which the water had flowed on the fire; but neither 
noise nor explosion, nor any dangerous consequences ensued. 
This boiler has some obvious defects. It is evident that 
thin flat plates are the form which, mechanically considered, 
is least favourable to strength; nor does it appear that any 
material advantage is gained to compensate for this by the 
magnitude of the surface exposed to the action of the fire. 
It is a great defect that a part of the surface of each of the 
plates is exposed to the action of the fire while it is out of 
contact with the water; in fact, in the upper part of the 
spaces marked e, fig. 66., steam only is contained. It has 
been observed by engineers, and usually shown by experi- 
ment, that if steam be heated on the surface of water it will 
be decomposed, and its elasticity destroyed ; this is not the 
only evil connected with the arrangement, for on this part 
of the metal, nevertheless, the fire acts^ — with less intensity, 
it is true, than on that part which contains the water, — but 
still with sufficient intensity to destroy the metal. Mr. 
Hancock appears to have attempted to remedy this defect 
by occasionally inverting the position of the flat chambers, 
placing that which at one time was at the bottom at the top, 
and vice versa. This may equalise the wear produced by 
the action of the fire upon the metal out of contact with 
water, but still the wear on the whole will not be less rapid. 
There appears to be no provision or space for separating the 
steam from the water with which it is charged ; in fact, there 
are no means in this engine of discharging the function of 
Mr. Gurney's separator. This will be found to produce 
considerable waste and loss of power in practice. 



238 THE STEAM ENGINE. 

The bars upon which the fire rests are of solid metal; and 
such is the intense heat to which they are subject, that, in 
an engine constantly at work, it is unlikely that they wilt 
last, without being renewed, more than about a week, if so 
much. The draft is maintained in this engine by means of 
a revolving fan worked by the engine. This, perhaps, is 
one of the greatest defects as compared - with other locomo- 
tives. The quantity of power requisite to work this bel- 
lows, and of which the engine is robbed, is very great. This 
defect is so fatal, that I consider it is quite impossible that 
the ingenious inventor can persevere in the use of it. Mr. 
Hancock has abandoned the use of the cranks "upon his 
working axle, and has substituted an endless chain and rag- 
wheels. This also appears to me defective, and a source by 
which considerable power is lost. On the other hand, how- 
ever, the weakness of the axle which is always produced/ by 
cranks is avoided. 

(111.) Mr. Nathaniel Ogle of Southampton obtained a 
patent for a locomotive carriage, and worked it for some 
time experimentally; but as his operations do not appear to 
have been continued, I suppose he was unsuccessful in ful- 
filling those conditions, without which the machine could" 
not be worked with economy and profit. In his evidence 
before a committee of the House of Commons, he has thus 
described his contrivance : — 

"The base of the boiler and the summit are composed of 
cross pieces, cylindrical within and square without; there 
are holes bored through these cross pieces, and inserted 
through the whole is an air tube. The inner hole of the 
lower surface, and the under hole of the upper surface, are 
rather larger than the other ones. Round the air tube is 
placed a small cylinder, the collar of which fits round the 
larger aperture on the inner surface of the lower frame, and 
the under surface of the upper frame-work. These are both 
drawn together by screws from the top; these cross pieces 
are united by connecting pieces, the whole strongly bolted 



LOCOMOTIVE ENGINES ON TURNPIKE ROADS. 239 

together; so that we obtain, in one tenth of the space, and 
with one tenth of the weight, the same heating surface and 
power as is now obtained in other and low-pressure boilers, 
with incalculably greater safety. Our present experimental 
boiler contains 250 superficial feet of healing surface in the 
space of 3 feet 8 inches high, 3 feet long, and 2 feet 4 inches 
broad, and weighs about 8 cwt. We supply the two cylin- 
ders with steam, communicating by their pistons with a 
crank axle, to the ends of which either one or both wheels 
are affixed, as may be required. One wheel is found to be 
sufficient, except under very difficult circumstances, and 
when the elevation is about one foot in six, to impel the ve- 
hicle forward. 

"The cylinders of which the boiler is composed are so 
small as to bear a greater pressure than could be produced 
by the quantity of fire beneath the boiler; and if any one of 
these cylinders should be injured by violence, or any other 
way, it would become merely a safety valve to the rest. 
We never, with the greatest pressure, burst, rent, or injured 
our boiler; and it has not once required cleaning, after hav- 
ing been in use twelve months." 

(112.) Dr. Church of Birmingham has obtained a suc- 
cession of patents for contrivances connected with a locomo- 
tive engine for stone roads; and a company, consisting of a 
considerable number of individuals, possessing sufficient ca- 
pital, has been formed in Birmingham for carrying into ef- 
fect his designs, and working carriages on his principle. 
The present boiler of Dr. Church is formed of copper. 
The w T ater is contained between two sheets of copper, 
united together by copper nails, in a manner resembling 
the way in which the cloth forming the top of a mattress or 
cushion is united with the cloth which forms the bottom of 
it, except that the nails or pins, which bind the sheets of 
copper, are much closer together. The water, in fact, seems 
to be " quilted" or " padded," in between two sheets of thin 
copper. This double sheet of copper is formed into an ob- 



240 THE STEAM ENGINE. 

long rectangular box, the interior of which is the fire-place 
and ash-pit, and over the end of which is the steam-chest. 
The great extent of surface exposed to the immediate action 
of the fire causes steam to be produced with great rapidity. 

An obvious defect which such a boiler presents is the dif- 
ficulty of removing from it any deposite or incrustation, 
which may collect between the sheets of copper so closely 
and intricately connected. Dr. Church proposes to effect 
this, when it is required, by the use of an acid, which will 
combine readily with the incrustation, and by which the 
boiler may therefore be washed. This method of cleansing 
boilers was recommended by Dr. Wollaston to Mr. Gurney, 
who informed me, however, that he found that it was not 
practicable in the way in which boilers must commonly be 
used. 

I apprehend, also, that the spaces between the sheets of 
copper, in Dr. Church's boiler just described, will hardly 
permit the steam bubbles which will be formed to escape 
with sufficient facility into the steam-chest; and being re- 
tained in that part of the boiler which is exposed to the ac- 
tion of the fire, the metal will be liable to receive an undue 
temperature. 

I have, however, seen this engine working, and its per- 
formance was very satisfactory. 

(113.) Various other projects for steam carriages on com- 
mon roads are in various degrees of advancement, among 
which may be mentioned those of Messrs. Maudslay and 
Field, Col. Macerone, and Mr. Russell of Edinburgh; but 
our limits compel us to omit any detailed account of them. 



241 



CHAPTER XII. 



STEAM NAVIGATION. 

Propulsion by paddle wheels. — Manner of driving them. — Marine Engine. 
— Its form and arrangement. — Proportion of its cylinder. — Injury to 
boilers by deposites and incrustation. — Not effectually removed by 
blowing out. — Mr. Samuel Hall's condenser. — Its advantages. — Origi- 
nally suggested by Watt. — Hall's steam saver. — Howard's vapour en- 
gine. — Morgan's paddle wheels. — Limits of steam navigation. — Propor- 
tion of tonnage to power. — Average speed. — Consumption of fuel. — 
Iron steamers.- — American steam raft. — Steam navigation to India. — 
By Egypt and the Red Sea to Bombay. — By same route to Calcutta.— . 
By Syria and the Euphrates to Bombay. — Steam communication with 
the United States from the west coast of Ireland to St. John's, Halifax, 
and New York. 

(114.) Among the various ways in which the steam en- 
gine has ministered to the social progress of our race, none 
is more important and interesting than the aid it has afforded 
to navigation. Before it lent its giant powers to that art, lo- 
comotion over the waters of the deep was attended with a 
degree of danger anduncertainty, which seemed so necessa- 
ry and so inevitable, that, as a common proverb, it became 
the type and representative of everything else which was 
precarious and perilous. The application, however, of steam 
to navigation has rescued the mariner from much of the 
perils of the winds and waves ; and even in its actual state, 
apart from the improvements which it is still likely to re- 
ceive, it has rendered all voyages of moderate length as safe 
and as regular as journeys over land. We are even now 
upon the brink of such improvements as will probably so ex- 
tend the powers of the steam engine, as to render it avail- 

31 



242 THE STEAM ENGINE. 

able as the means of connecting the most distant points of 
the earth. 

The manner in which the steam engine is commonly ap- 
plied to propel vessels must be so familiar as to require but 
short explanation. A pair of wheels, like common under- 
shot water-wheels, bearing on their rims a number of flat 
boards called paddle boards, are placed one at each side of 
the vessel, in r such a position that when the vessel is im- 
mersed to her ordinary depth the lowest paddle boards shall 
be submerged. These wheels are fixed upon a shaft, which 
is made to revolve by cranks placed upon it, in the same 
manner as the fly wheel of a common steam engine is turned. 
It is now the invariable custom to place in steam vessels two 
engines, each of which works a crank : these two cranks 
are placed at right angles to each other, in the same manner 
as the cranks already described upon the working axles of 
locomotive engines. When either crank is at its dead point, 
the other is in full activity, so that the necessity for a fly 
wheel is superseded. The engines may be either condens- 
ing or high-pressure engines ; but in Europe the low-pres- 
sure condensing engine has been invariably used for nautical 
purposes. In the United States, where steam navigation 
had its origin, and where it was, until a recent period, much 
more extensively practised than in Europe, less objection 
was felt to the use of high-pressure engines ; and their limit- 
ed bulk, their small original cost, and simplicity of structure, 
strongly recommended them, more especially for the pur- 
poses of river navigation. 

(g.) The original type of nearly all the engines used in 
steam navigation was that constructed at Soho by Watt and 
Bolton for Mr. Fulton, and first used by him upon the Hud- 
son river. This had the beam below the piston rod as in 
the English boal-engines, but the cylinder above deck, as in 
the American. From this primitive form, the two nations 
have diverged in opposite directions. The Americans, na- 
vigating rivers, and having speed for their principal object, 



STEAM NAVIGATION. 243 

have not hesitated to keep the cylinder above deck, and have 
lengthened the stroke of the piston in order to make the 
power cut on a more advantageous point of the wheel. Com- 
pactness has been gained by the suppression of the working 
beam. 

On the other hand, the English, having the safe navigation 
of stormy seas as their more important object, have shortened 
the cylinder in order that the piston rod may work wholly, 
under the deck, and the arrangement of Fulton's working 
beam has been retained by them. In this way there can be 
no doubt, that they have lost the power of obtaining equal 
speed from a given expenditure of power, and those conver- 
sant in the practice and theory of stowing ships may well 
doubt whether security is not also sacrificed. — a. e. 

The arrangement of the parts of the maritime engine dif- 
fers in some respects, from that of the land engine. Want 
of room renders greater compactness necessary ; and in or- 
der to diminish the height of the machine, the working beam 
is transferred from above the cylinder to below it. In fact, 
there are two beams, one at each side of the engine, which 
are connected by a parallel motion with the piston, the rods 
of the parallel motion extending from the lower part of the 
engine to the top of the piston rod. The working end of 
the beam is connected with the crank by a connecting rod, 
presented upwards instead of downwards, as in the land en- 
gine. The proportion of the length and diameters of the cy- 
linders differ from those of land engines for a like reason : 
to save height, short cylinders with large diameters are used. 
Thus, in an engine of 200 horse power, the length of the cy- 
linder is sometimes 60 inches, and its diameter 53 inches : 
the valves and the gearing which work them, the air pump, 
condenser, and other parts of the machine, do not differ ma- 
terially from those already described in the land engines. 

(A.) The action of machinery may be rendered more equa- 
ble by using two engines, each of half the power, instead, of 
a single one. If one of these be working with its maximum 



244 THE STEAM ENGINE. 

force when the other is changing the direction of its motion, 
the result of their joint action will be a force nearly constant. 
Such a combination was invented by Mr. Francis Ogden, 
and has been used in several steam boats constructed under 
his directions. It would however be far more valuable in 
other cases, particularly where great uniformity in the ve- 
locity is indispensable. 

This method has now become almost universal in the en- 
gines used in the English steam boats, each of which has 
usually two, both applied to the same shaft, and therefore 
capable of being used singly or together to turn the paddle 
wheels. In the American steam boats, although two engines 
have been often applied, each usually acts upon no more 
than one of the wheels. We can see no other good reason 
for this, than that our engineers do not wish to be thought to 
copy Mr. Ogden. — a. e. 

The nature of the work which the marine engine has to 
perform, is such, that great regularity of action is neither ne- 
cessary nor possible. The agitation of the surface of the sea 
will cause the immersion of the paddle wheels to vary very 
much, and the resistance to the engine will undergo a cor- 
responding change : the governor, and other parts of the ap- 
paratus already described, contrived for imparting to the en- 
gine that extreme regularity which is indispensable in its ap- 
plication to manufactures, are therefore here omitted ; and 
nothing is introduced except what is necessary to maintain 
the engine in its full working power. 

It is evident that it must be a matter of considerable im- 
portance to reduce the space occupied by the machinery on 
board a vessel to the least possible dimensions. The marine 
boilers, therefore, are constructed so as to yield the necessary 
quantity of steam with the smallest practical dimensions. 
With this view a much more extensive surface in propor- 
tion to the size of the boiler is exposed to the action of the 
fire. In fact, the flues which carry off the heated air to the 
chimney are conducted through the boiler, so as to act upon 



STEAM NAVIGATION. 245 

the water on every side in thin oblong shells, which traverse 
the boiler backward and forward repeatedly, until finally 
they terminate in the chimney. By this arrangement the 
original expense of the boilers is very considerably increased; 
but, on the other hand, their steam-producing power is also 
greatly augmented ; and from experiments lately made by 
Mr. Watt at Birmingham, it appears that they work with 
an economy of fuel compared with common land boilers in 
the proportion of about two to three. Thus they have the 
additional advantage of saving the tonnage as well as the ex- 
pense of one third of the fuel. 

One of the most formidable difficulties which has been en- 
countered in applying the steam engine to. the purposes of 
navigation has arisen from the necessity of supplying the 
boiler with sea water, instead of pure fresh water. This wa- 
ter (also used for the purpose of condensation) being inject- 
ed into the condenser and mixed with the condensed steam, 
is conducted as feeding water into the boiler. 

The salt contained in the sea water, not being evaporated, 
remains in the boiler. In fact, it is separated from the water 
in the same manner as by the process of distillation. As 
the evaporation in the boiler is continued, the proportion of 
salt contained in the water is, therefore, constantly increased, 
until a greater proportion is accumulated than the water is 
capable of holding in solution ; a deposition of salt then 
commences, and is lodged in the cavities at the bottom of 
the boiler. The continuance of this process, it is evident, 
would at length fill the boiler with salt. 

But besides this, under some circumstances, a deposition 
of lime* is made, and a hard incrustation is formed on the 
inner surface of the boiler. In some situations, also, sand 
and mud are received into the boiler, being suspended in 
the water pumped in for feeding it. All these substances, 

* Ten thousand grains of pure sea water contain muriate of soda 
220 grs., sulphate of soda 33 grs., muriate of magnesia 42 grs., and 
muriate of lime 8 grs. 



246 THE STEAM ENGINE. 

whether deposited in a loose form in the lower parts of the 
boiler or collected in a crust on its inner surface, form ob- 
structions to the passage of heat from the fire to the water. 
The crust thus formed is not unfrequently an inch or more 
in thickness, and so hard that good chisels are broken in re- 
moving it. The heat more or less intercepted by these sub- 
stances collects in the metal of the boiler, and raises it to a 
temperature far exceeding that of the water within. It may 
even, if the incrustation be great, be sufficient to render the 
boiler red-hot. These circumstances occasion the rapid wear 
of the boiler, and endanger its safety by softening it. 

The remedy which has generally been adopted to remove 
or diminish these injurious effects consists in allowing a 
stream of hot water continually to flow from the boiler, and 
supplying from the feed-pipe a corresponding portion of 
cold water. While the hot water which flows from the 
boiler in this case contains, besides its just proportion of salt, 
that portion which has been liberated from the water con- 
verted into vapour, the cold water which is supplied through 
the feed-pipe contains less than its just proportion of salt, 
since it is composed of the natural sea water, mixed with- the 
condensed steam, which latter contains no salt. In this 
manner, the proportion of the salt in the boiler may be pre- 
vented from accumulating; but this is attended with con- 
siderable inconvenience and loss. It is evident that the 
discharge of the hot water, and the introduction of so con- 
siderable a quantity of cold water, entails upon the machine 
a great waste of fuel, and, consequently, renders it neces- 
sary that the vessel should be supplied with a much larger 
quantity of coals than are merely necessary for propelling 
it. In long voyages, where this inconvenience is most felt, 
this is a circumstance of obvious importance. But besides 
the waste of fuel, the speed of the vessel is diminished by 
the rate of evaporation in the boiler being checked by the 
constant stream of cold water flowing into it. This process 
of discharging the water, which is called blowing out, is 



STEAM NAVIGATION. 247 

only practised occasionally. In the Admiralty steamers, 
the engineers are ordered to blow out every two hours. 
But it is more usual to do so only once a day. 

This method, however, of blowing out furnishes but a 
partial remedy for the evils we have alluded to: a loose de- 
posite will perhaps be removed by such means, but an in- 
crustation, more or less according to the circumstances and 
quality of the water, will be formed; besides which, the 
temptation to work the vessel with efficiency for the moment 
influences the engine men to neglect blowing out; and it is 
found that this class of persons can rarely be relied upon to 
resort to this remedy with that constancy and regularity 
which are essential for the due preservation of the boilers. 
The class of steam vessels which, at present, are exposed to 
the greatest injury from these causes are. the sea-going 
steamers employed by the Admiralty; and we find, by a 
report made by Messrs. Lloyd and Kingston to the Admi- 
ralty, in August, 1834, that it is admitted that the method 
of blowing out is, even when daily attended to, ineffectual. 
" The water in the boiler," these gentlemen observe. ** is 
kept from exceeding a certain degree of saltness, by periodi- 
cally blowing a portion of it into the sea ; but whatever care 
is taken, in long voyages especially, salt will accumulate, 
and sometimes in great quantities and of great hardness, so 
that it is with difficulty it can be removed. Boilers are 
thus often injured as much in a few months as they would 
otherwise be in as many years. The other evil, necessarily 
resulting from this state of things is, besides the rapid de- 
struction of the boilers, a great waste of fuel, occasioned by 
the difficulty with which the heat passes through the incrus- 
tation on the inside, by the leaks which are thereby caused, 
and by the practice of blowing out periodically, as before 
mentioned, a considerable portion of the boiling water." 

It would be impracticable to carry on board the vessel a 
sufficient quantity of pure fresh water to work the engine 
exclusively by its means. To accomplish this, it would be 



248 THE STEAM ENGINE. 

necessary to have a sufficient supply of cold water to keep 
the condensing cistern cold, to supply the jet in the con- 
denser, and to have a reservoir in which the warm water 
coming from the waste pipe 6f the cold cistern might be 
allowed to cool. Engineers have therefore directed their 
attention to some method by which the steam may be con- 
densed without a jet, and after condensation be preserved 
for the purpose of feeding the boiler. If this could be ac- 
complished, it would not be necessary to provide a greater 
quantity of pure water than would be sufficient to make up 
the small portion of waste which might proceed from leak- 
age and from other causes; and it is evident that this portion 
might always be readily obtained by the distillation of sea 
water, which might be effected by a small vessel exposed to 
the same fire which acts upon the boiler. 

(115.) Mr. Samuel Hall of JBasford, near Nottingham, 
has taken out patents for a new form of condenser, contrived 
for the attainment of these ends, besides some other im- 
provements in the engine. 

The condenser of Mr. i^a// consists of a great number of 
narrow tubes immersed in a cistern of cold water : the steam 
as it passes from the cylinder, after having worked the pis- 
ton, enters these tubes, and is immediately condensed by 
their cold surfaces. It flows in the form of water from their 
remote extremities, and is drawn off by the air-pump, and 
conducted in the usual way to a cistern from which the 
boiler is fed. In the marine engines constructed under Mr. 
Hall's patents, the tubes of the condenser being in an up- 
right or vertical position, the steam flows from the cylinder 
into the upper part of the condenser, which is a low flat 
chamber, in the bottom of which is inserted the upper ex- 
tremities of the tubes, through which the steam passes down- 
wards, and as it passes is condensed. It flows thence into a 
similar chamber below, from whence it is drawn off by the 
air-pump. 

It is evident that at sea an unlimited supply of cold water 



STEAM NAVIGATION. 249 

may be obtained to keep the condensing cistern cold, so that 
a perfect condensation may always be effected by these 
tubes, if they be made sufficiently small. The water formed 
by the condensed steam will be pure distilled water; and if 
the boiler be originally filled with water which does not 
hold in solution any earthy or other matter which might be 
deposited or encrusted, it may be worked for any length of 
time without injury. The small quantity of waste from 
leakage is supplied in Mr. Hall's engine by a simple appa- 
ratus in which a sufficient quantity of sea water may be dis- 
tilled. 

The following are the advantages, as stated by Mr. Hall, 
to be gained by his condenser : — 

1. A saving of fuel, amounting in some cases to so much 
as a third of the ordinary consumption. 

2. The preservation of the boilers from the destruction 
produced in common engines by the corrosive action of sea 
or other impure water, and by encrustations of earthy mat- 
ter. 

3. The saving of the time spent in cleaning the boilers. 

4. A considerable increase of power, owing to the clean- 
ness of the boilers ; the absence of injected water to be 
pumped out of a vacuum; the greater perfection of the va- 
cuum ; the better preservation of the piston and valves of the 
air-pump; and (by another contrivance of his) the more per- 
fect lubrication of the parts of the engine. 

5. The water in the boiler being constantly maintained at 
the same height by- self-acting arrangement. 

6. The size of a boiler exerting a given power, being 
much smaller than the common kind, owing to its more per- 
fect action. 

Messrs. Lloyd and Kingston were employed by govern- 
ment to examine and report the effects of Mr. Hall's boilers, 
and they stated in their report, already referred to, that the 
result is so successful as to leave nothing to be wished for. 
Among the advantages which they enumerate are the in- 

32 



250 THE STEAM ENGINE. 

creased durability of the engines; the prevention of acci- 
dents through carelessness, or otherwise, arising from the 
condenser and air-pump becoming choked with injection 
water; and the additional security against the boilers being 
burnt in consequence of the water being suffered to get too 
low. But the greatest advantages, compared with which 
they consider all others to be of secondary importance, are 
the increased durability of the boilers and the saving of 
fuel. 

About 16 engines, built either wholly upon Mr. Hall's 
principle or having his condenser attached to them, have 
now (October, 1835) been working in different parts of Eng- 
gland, and on board different vessels for various periods, 
from three years to three months; and it appears from the 
concurrent testimony of the proprietors and managers of 
them, that they are attended with all the -advantages which 
the patentee engaged for. The part of the contrivance the 
performance of which would have appeared most doubtful 
would have been the maintenance of a sufficiently good va- 
cuum in the condenser, in the absence of the usual method 
of condensation by the injection of cold water; nevertheless 
it appears that a better vacuum is sustained in these engines 
than in the ordinary engines which condense by jet. The 
barometer gauge varies from 29 to 29£ inches, and in some 
cases comes up to 30 inches, according to the state of the 
barometer: this is a vacuum very nearly perfect, and indeed 
may be said to be so for all practical purposes. The Prince 
Llewellyn and the Jlir steam packets, b3longing to the St. 
George Steam Packet Company, have worked such a pair 
of these engines for about a year. The City of London 
steam packet, the property of the General Steam Navigation 
Company, has been furnished with two fifty-horse engines, 
and has worked them during the same period. In all cases 
the boilers have been found perfectly free from scale or in- 
crustation; and the deposite is either absolutely nothing or 
very trifling, requiring the boiler to be swept about once in 



STEAM NAVIGATION 251 

half a year, and sometimes not so often. The trial which 
has been made of these engines in the navy has proved satis- 
factory, so far as it has been carried. The Lords of the Ad- 
miralty have lately ordered a pair of seventy-horse engines 
to b» constructed on this principle for a vessel now (Octo- 
ber, 1835) in process of construction ;* and another vessel 
in all respects similar, except having copper boilers, is like- 
wise ordered ; so that a just comparison may be made. It 
would, however, have been more fair if both vessels had 
been provided with iron boilers, since copper does not re- 
ceive incrustation as readily ;<s iron. 

It would seem that the advantages of these boilers in the 
vessels of the St. George Steam Packet Company were re- 
garded by the directors as sufficiently evident, since, after 
more than a year's experience, they are about to place a pair 
of ninety-horse engines of this kind in a new and powerful 
steamer called the Hercules. 

Engines furnished with Mr. Hall's apparatus have not 
yet, so far as I am informed, been tried with reference to 
the power exerted by the consumption of a given quantity 
of fuel. The mere fact of a good vacuum being sustained in 
the condenser cannot by itself be regarded as a conclusive 
proof of the efficiency of the engine, without the water or 
air introduced by a condensing jet. Mr. Hall, nevertheless, 
uses as large an air pump as that of an ordinary condensing 
engine, and recommends even a larger one. For what pur- 
pose, it may be asked, is such an appendage introduced ? If 
there be nothing to be removed but the condensed steam, a 
very small pump ought to be sufficient. It is not wonder- 
ful that a good vacuum is sustained in the condenser, if the 
power expended on the air pump is employed in pumping 
away uncondensed steam. Such a contrivance would be 
merely a deception, giving an apparent but no real advan- 
tage to the engine. 

* This order has, as Mr. Hall informs me, been given without requiring 
any guarantee as to the performance of the engines. 



252 THE STEAM ENGINE. 

Having mentioned these advantages, which are said to 
arise from Mr. Hall's condenser, it is right to slate that it is 
in fact a reproduction of an early invention of Mr. Watt. 
There is in possession of James Watt, esquire, a drawing of 
a condenser laid before parliament in 1776, in which the 
same method of condensing without a jet is proposed. Mr. 
Watt, however, finding that he could not procure by that 
means so sudden or so perfect a vacuum as by injection, 
abandoned it. I believe he also found that the tubes of the 
condenser became furred with a deposite which impeded the 
process of condensation. It would seem, however, that 
Mr. Hall has found means to obviate these effects. It is 
right to add, that Mr. Hall, in his specification, distinctly 
disclaims all claim to the method of condensing by tubes 
without jet. 

There is another part of Mr. Hall's contrivance which 
merits notice. In all engines, a considerable quantity of 
steam is allowed to escape from the safety valve. Whenever 
the vessel stops, the steam, which would otherwise be taken 
from the boiler by the cylinders, passes out through this 
valve into the atmosphere. Also, whenever the cylinders 
work at under-power, and do hot consume the steam as fast 
as it is produced by the boiler, the surplus steam escapes 
through the valve. Now, according to the principle of Mr. 
Hall's method, it is necessary to save the water which thus 
escapes in vapour, since otherwise the pure water of the 
boiler would be more rapidly wasted. Mr. Hall accordingly 
places a safety valve of peculiar construction in communica- 
tion with a tube which leads to the condenser, so that when- 
ever, either by stopping the engine or diminishing its work- 
ing power, steam accumulates in the boiler, its increased 
pressure opens the safety valve, and it passes through this 
pipe to the condenser, where it is reconverted into water, 
and pumped off by the air-pump into the cistern from which 
the boiler is fed. 

The attainment of an object so advantageous as to extend 



STEAM NAVIGATION. 253 

the powers of steam navigation, and to render the perform- 
ance of voyages of any length practicable, so far as the effi- 
ciency of the machinery is concerned, has naturally stimu- 
lated the inventive genius of the country. The preservation 
of the boiler by the prevention of deposite and incrustation is 
an object of paramount importance; and its attainment ne- 
cessarily involves, to a certain degree, anoiher condition on 
which the extension of steam voyages must depend, viz. the 
economy of fuel. In proportion as the economy of fuel is 
increased, in the same proportion will the limit to which 
steam navigation may be carried be extended. 

(116.) A patent has been obtained by Mr. Thomas 
Howard of London for a form of engine possessing much 
novelty and ingenuity, and having pretensions to the attain- 
ment of a very extraordinary economy of fuel, in addition 
to those advantages which have been already explained as 
attending Mr. Hall's engines. In these engines, as in Mr. 
Hall's, the steam is constantly reproduced from the same 
water, so that pure or distilled water may be used; but. Mr. 
Howard dispenses with the use of a boiler altogether. The 
steam also with which he works is in a state essentially dif- 
ferent from the steam used in ordinary engines. In these, 
the vapour is raised directly from the water in a boiling 
state, and it contains as much water as it is capable of hold- 
ing at its temperature. Thus, at the temperature of 212°, a 
cubic foot of steam used in common- engines will contain 
about a cubic inch of water; but in the contrivance of Mr. 
Howard, a considerable quantity of heat is imparted to the 
steam before it passes into the cylinder in addition to what 
is necessary to maintain it in the vaporous form. 

A quantity of mercury is. placed in a shallow wrought- 
iron vessel over a coke fire, by which it is maintained at the 
temperature of from 400° to 500°. The surface exposed to 
the fire is three fourths of a square foot for each horsepower. 
The upper surface of the mercury is covered by a very thin 
plate of iron, which rests in contact with it, and which is so 



254 THE STEAM ENGINE. 

contrived as to present about four times as much surface as 
that exposed beneath to the fire. Adjacent to this a vessel 
of water is placed, kept heated nearly to the boiling point, 
which communicates by a nozzle and valve with the chamber 
or vessel immediately above the mercury. At intervals 
corresponding to the motion of the piston, a small quantity 
of water is injected from this vessel, and thrown upon the 
plate of iron which rests upon the hot mercury: from this it 
receives the heat necessary not only to convert it into steam, 
but to expand that steam, and raise it to a temperature above 
the temperature it would receive if raised in immediate 
contact with water. In fact, the steam thus produced will 
have a temperature not corresponding to its pressure, but 
considerably above that point, and it will therefore be in 
circumstances under which it will part with more or less of 
its heat, and allow its temperature to be lowered without 
being even partially condensed, whereas steam used in the 
ordinary steam engines must be more or less condensed by 
the slightest diminution of its temperature. The quantity 
of liquid injected into the steam chamber must be regulated 
by the power at which the engine is intended to • work. 
The fire is supplied with air by a blowing machine, which 
is subject to exact regulation. The steam, produced in the 
manner already explained, passes into a chamber which sur- 
rounds the working cylinder ; and this chamber itself is 
enclosed by another space, through which the air from the 
furnace must pass before it reaches the flue. In this way it 
imparts its redundant heat to the steam which is about to 
work the cylinder, and raises it to a temperature of about 
400° ; the pressure, however, not exceeding 25 lbs. per 
square inch. The arrangement of valves for the admission 
of the steam to the cylinder is such as to cause the steam to 
act expansively. 

The vacuum on the opposite side of the piston is main- 
tained by condensation in the following manner : — The con- 
denser is a copper vessel placed in a cistern constantly sup- 



STEAM NAVIGATION. 255 

plied with cold water, and the steam flows to it from the 
cylinder by an eduction pipe in the usual way : a jet is ad- 
mitted to it from an adjacent vessel, which, before the en- 
gine commences work, is filled with distilled water ; the con- 
densing water and condensed steam are pumped from the 
condenser by air-pumps of the usual construction, but small- 
er, inasmuch as there is no air to be withdrawn, as in com- 
mon engines. The warm water thus pumped out of the con- 
denser is driven into a copper pipe or worm, which is car- 
ried with many coils through a cistern of cold water, so that 
when it arrives at the end of this pipe it is reduced to the 
common temperature of the atmosphere. The pipe is then 
conducted into the vessel of distilled water already mention- 
ed, and the water flowing from it continually replaces the 
water which flows into the condenser through the conden- 
sing jet. The condensing water being purged of air, a very 
small air pump is sufficient ; since it has only to exhaust the 
condenser and tubes at starting, and to remove whatever air 
may enter by casual, leakage. The patentee states that the 
condensation takes place as rapidly and as perfectly as in the 
best steam engine, and it is evident that this method of con- 
densation is applicable even where the mercurial generator 
already described may not be employed. The vessel from 
which the water is injected into the mercurial generator is 
likewise fed by the air-pump connected with the condenser. 
There is another pipe besides the copper worm already de- 
scribed, which is carried from the hot well to this vessel, 
and the water is of course returned through it without being 
cooled. This vessel is likewise sufficiently exposed to the 
action of the fire to maintain it at a temperature somewhat 
below the boiling point. 

An apparatus of this construction was in the spring of the 
present year (1835) placed in the Admiralty steamer called 
the Comet, in connexion with a pair of 40-horse engines. 
The patentee states that these engines were ill adapted to the 
contrivance ; nevertheless, the vessel was successfully work- 



256 THE STEAM ENGINE. 

ed in the Thames for 800 miles : she also performed a voy- 
age from Falmouth to Lisbon, but was prevented from re- 
turning by an accident which occurred to the machinery 
near the latter port. In this experimental voyage, the con- 
sumption of fuel is stated never to have exceeded a third of 
her former consumption, when worked by Bolton and Watt's 
engines; the former consumption of coals being about 800 
lbs. per hour, and the consumption with Mr. Howard's en- 
gine being under 250 lbs. of coke per hour. 

After this failure (which, however, was admitted to be 
one of accident and not of principle) the government did not 
consider itself justified in bestowing further lime or incur- 
ring greater expense in trying this engine. Mr. Howard, 
however, has himself built a new vessel, in which he is 
about to place a pair of forty-horse engines. This vessel is 
now (December, 1835) nearly ready, and will bring the 
question to issue by a fair experiment. The advantages of 
the contrivance as enumerated by the patentee are : — 

First, The small space and weight occupied by the ma- 
chinery, arising from the absence of a boiler. 
Secondly, The diminished consumption- of fuel. 
Thirdly, The reduced size of the flues. 
Fourthly, The removal of the injurious effects arising 
from deposite and incrustation. 
Fifthly, The absence of smoke. 

Some of these improvements, if realized, will be attended 
with important advantages in steam navigation. Steamers 
of a given tonnage and power will have more disposable 
space for lading and fuel, and in short voyages may carry 
greater freight, or an increased number of passengers ; or 
by taking a larger quantity of fuel,* may make greater runs 

* The fuel used in this form of engine is coke, and not coal. A ton of coke 
occupies the same space as two tons of coal ; the saving of tonnage, there- 
fore, by the increased economy of fuel will not be in so great a propor- 
tion as the saving of fuel. A quantity of fuel of equivalent power will 
occupy about half the present space, but the displacement or immersion 
which it produces will be only one fourth of its present effect. 



STEAM NAVIGATION. 257 

than are now attainable ; or, finally, with the same tonnage 
and the same lading, they may be supplied with more pow- 
erful machinery. 

(117.) To obtain from the moving power its full amount of 
mechanical effect in propelling the vessel, it would be necessa- 
ry that its force should propel, by constantly acting against the 
water in a horizontal direction, and with a motion contrary to 
the course of the vessel. No system of mechanical propellers 
has, however, yet been contrived capable of perfectly attain- 
ing this end. Patents have been granted for many ingeni- 
ous mechanical combinations to inipart to the propelling sur- 
faces such angles as appeared to the respective contrivers 
most advantageous. In most of these, however, the me- 
chanical complexity has formed a fatal objection. No part 
of the machinery of a steam vessel is so liable to become de- 
ranged at sea as the paddle wheels ; and, therefore, such sim- 
plicity of construction as is compatible with those repairs 
which are possible on such emergencies is quite essential for 
safe practical use. 

The ordinary paddle wheel, as I have already stated, is a 
wheel revolving upon a shaft driven by the engine, and car- 
rying upon its circumference a number of flat boards, called 
paddle boards, which are secured by nuts or braces in a fixed 
position ; and that position is such that the planes of (he pad- 
dle boards diverge nearly from the centre of the shaft on 
which the wheel turns. The consequence of this arrange- 
ment is that each paddle board can only act in that direction 
which is most advantageous for the propulsion of the vessel 
when it arrives near the lowest point of the wheel. In 
figure 67. let o be the shaft on which the common paddle 



•33 



258 



THE STEAM ENGINE. 



Fig. 67. 




wheel revolves; the position of the paddle boards are repre- 
sented at a, b, c, &c. ; x, y represents the water line, the 
course of the vessel being supposed to be from x to y; the 
arrows represent the direction in which the paddle wheel re- 
volves. The wheel is immersed to the depth of the lowest, 
paddle board, since a less degree of immersion would render 
a portion of the surface of each paddle board mechanically 
useless. In the position a the whole force of the paddle 
board is efficient for propelling the vessel ; but. as the pad- 
dle enters the water in the position h, its action upon the 
water, not being horizontal, is only partially effective for pro- 
pulsion : a part of the force which drives the paddle is ex- 
pended in depressing the vyater, and the remainder in driv- 
ing it contrary to the course of the vessel, and, therefore, by 
its reaction producing a certain propelling effect. The ten- 
dency, however, of the paddle entering the water at h, is to 
form a hollow or trough, which the water, by its ordinary 
properly, has a continual tendency to fill up. After passing 
the lowest point a, as the paddle approaches the position b, 
where it emerges from the water, its action again becomes 
oblique, a part only having a propelling effect, and the re- 



STEAM NAVIGATION. 259 

mainder having a tendency to raise the water, and throw up 
a wave and spray behind the paddle wheel. It is evident 
that the more deeply the paddle wheel becomes immersed 
the greater will be the proportion of the propelling power 
thus wasted in elevating and depressing the water ; and, if 
the wheel were immersed to its axis, the whole force of the 
paddle boards, on entering and leaving the water, would be 
lost, no part of it having a tendency to propel. If a still 
deeper immersion takes place, the paddle boards above the 
axis would have a tendency to retard the course of the ves- 
sel. When the vessel is, therefore, in proper trim, the im- 
mersion should not exceed nor fall short of the depth 
of the lowest paddle ; but for various reasons it is im- 
possible in practice to maintain this fixed immersion : the 
agitation of the surface of the sea, causing the vessel to roll, 
will necessarily produce a great variation in the immersion 
of the paddle wheels, one becoming frequently immersed to 
its axle, while the other is raised altogether out of the water. 
Also the draught of water of the vessel is liable to change, 
by the variation in her cargo: this will necessarily happen 
in steamers which take long voyages. At starting they are 
heavily laden with fuel, which as they proceed is gradually 
consumed, whereby the vessel is lightened ; and it does not 
appear that it is practicable to use sea water as ballast to re- 
store the proper degree of immersion. 

(118.) Among the contrivances which have been pro- 
posed for remedying these defects of the common paddle 
wheel by introducing paddle boards capable of shifting their 
position as they revolve with the circumference of the wheel, 
the only one which has been adopted to any considerable 
extent in practice is that which is commonly known as Mor- 
gan's Paddle Wheel. The original patent for this contriv- 
ance was granted to Elijah Galloway, and sold by him to 
Mr. William Morgan. Subsequently to the purchase some 
improvements in its structure and arrangements were intro- 
duced, and it is now extensively adopted by Government in 



260 THE STEAM ENGINE. 

the Admiralty steamers. It was first tried on board His 
Majesty's steamer the Confiance ; and after several suc- 
cessful experiments was ordered by the Lords of the Admi- 
ralty to be introduced on board the Flamer, the Firebrand, 
the Columbia, the Spitfire, the Lightning, a large war 
steamer called the Medea,* the Tartarus, the Blazer, 
&c. It has been tried by Government in several well-con- 
ducted experiments, where two vessels of precisely the same 
model, supplied with similar engines of equal power, and 
propelled, one by Morgan's paddle wheels, and the other by 
the common paddle wheels; when it was found that the ad- 
vantage of the former, whether in smooth or in rough wa- 
ter, was quite apparent. One of the commanders in these 
experiments (Lieutenant Belson) states that the improve- 
ment in the speed of the Confiance, after being supplied 
with these wheels, was proportionately greater in a sea way 
than in smooth water ; that their action was not impeded by 
the waves, since the variation of the velocity of the engine 
did not exceed one or two revolutions per minute : the ves- 
sel's way was never stopped, and there was no sensible in- 
crease of vibration on the paddle boxes during the gale. 
Another commander reported that on a comparison of the 
Confiance and a similar and equally powerful vessel, the 
Carron, the Confiance performed in fifty-four hours the 
voyage which occupied the Carron eighty-four hours in 
running. Independently of the great saving of fuel effected 
(namely, ten bushels per hourt), or the time saved in run- 
ning the same distance, other advantages have been secured 

* This splendid ship is 860 tons burden, with engines of 220 horse 
power. 

f See Report quoted in Mechanic's Magazine, vol. xxii. p. 275. This 
saving cannot amount to less than 40 per cent, upon the whole consump- 
tion of fuel; it certainly is considerably beyond what I should have con- 
ceived to be possible; but I have no reason to doubt the accuracy of the 
Report. I estimate the former consumption at 10 pounds per horse 
power per hour, which on 220 horse power would be 2200 pounds, of 
which 840 pounds =» 10 bushels, would be about 4-10ths. 



STEAM NAVIGATION. 261 

by the modification in question. On a comparison of the 
respective logs of the two vessels, it appeared that the Con- 
fiance had gained by the alteration in her wheels an in- 
crease of speed amounting to 2 knots on 7 in smooth water, 
and 2j knots on 4 to Ah knots in rough weather; that the 
action of the paddles did not bring up the engine or retard 
their velocity in a head sea; that in rolling their action as- 
sisted in righting the vessel; and that the wear and strain, 
as well on the vessel as on the engines, were materially re- 
duced. With respect to the durability of these wheels, the 
commander of the Fiamer reported in January, 1834, that 
in six weeks of the most tempestuous weather they found 
them to act remarkably well, without even a single float be- 
ing shifted. * 

This paddle wheel is represented in figure 68. The con- 
trivance may be shortly stated to consist in causing the wheel 
which bears the paddles to revolve on one centre, and the 
radial arms which move the paddles to revolve on another 
centre. Let ABCitEPGHibe the polygonal circumfe- 
rence of the paddle wheel, formed of straight bars, securely 
connected together at the extremities of the spokes or radii 
of the wheel which turns on the shaft which is worked by 
the engine ; the centre of this wheel being at o. So far this 
wheel is similar to the common paddle wheel ; but the pad- 
dle boards are not, as in the common wheel, fixed at A b c, 
&c, so as to be always directed to the centre o, but are so 
placed that they are capable of turning on axles which are 
always horizontal, so that they can take any angle with re- 
spect to the water which may be given to them. From the 
centres, or the line joining the pivots on which these paddle 
boards turn, there proceed short arms x, firmly fixed to the 

* See a more detailed account of these reports in the Mechanic's Ma- 
gazine, vol. xxii. p. 274., from which I have taken the drawing of this 
paddle wheel; and also see Report of the Committee of the House of 
Commons on Steam Navigation to India, Evidence of "William Morgan, 
p. 95. 



262 THE STEAM ENGINE. 

paddle boards at an angle of about 120°. On a motion given 
to this arm k, it will therefore give a corresponding angular 
motion to the paddle board, so as to make it turn on its 
pivots. At the extremities of the several arms marked k is 
a pin or pivot, to which the extremities of the radial arms 
l are severally attached, so that the angle between each ra- 
dial arm l and the short paddle arm k is capable of being 
changed by any motion imparted to l; the radial arms l are 
connected at the other end with a centre p, round which 
they are capable of revolving. Now since the points a b c, 
&c, which are the pivots on which the paddle boards turn, 
are moved in the circumference of a circle, of which the 
centre is o, they are always at the same distance from that 
point; consequently they will continually vary their dis- 
tance from the other centre p. Thus, when a paddle board 
arrives at that point of its revolution at which the centre p 
lies precisely between it and the centre o, its distance from 
p is less than in any other position. As it departs from that 
point, its distance from the centre p gradually increases until 
it arrives at the opposite point of its revolution, where the 
centre o is exactly between it and the centre p ; then the 
distance of the paddle board from the centre p is greatest. 
This constant change of distance between each paddle board 
and the centre p is accommodated by the variation of the 
angle between the radial arm l and the short paddle board 
arm k; as the paddle board approaches the centre p this 
gradually diminishes; and as the distance of the paddle 
board from p increases, the angle is likewise augmented. 
This change in the magnitude of the angle, which thus ac- 
commodates the varying position of the paddle board with 
respect to the centre p, will be observed in the figure. The 
paddle board d is nearest to p; and it will be observed that 
the angle contained between l and k is there very acute; at 
e the angle between l and k increases, but is still acute; at 
f it increases to a right angle; at a it becomes obtuse; and 
at k, where it is most distant from the centre p, it becomes 



STEAM NAVIGATION. 263 

most obtuse. It again diminishes at I, and becomes a right 
angle between a and b. Now this continual shifting of the 
direction of the short arm k is necessarily accompanied by 
an equivalent change of position in the paddle board to 
which it is attached; and the position of the second centre 
p is, or may be, so adjusted that this paddle board, as it en- 
ters the water and emerges from it, shall be such as shall be 
most advantageous for propelling the vessel, and therefore 
attended with less of that vibration which arises chiefly from 
the alternate depression and elevation of the water, owing to 
the oblique action of the paddle boards.* 

(i) The relative value of the two wheels, namely, the 
common paddle-wheel, and that of Morgan has been inves- 
tigated by Professor Barlow of the Military School, at 
Woolwich, and the results published in a paper of much 
ability in the Philosophical Transactions for 1834. By 
this paper it appears, that, when the paddles are not wholly 
immersed, the wheel of Morgan has no important advantage 
over the other, and only acquires one when the wheel wal- 
lows. But the most important of his inferences is that the 
common paddle is least efficient when in a vertical position, 
contrary to the usual opinion. From this we have a right 
to infer that the search for a form of wheel w T hich shall always 
keep the paddle vertical is one whose success need not be 
attended with any important consequence. The superior 
qualities of Morgan's wheel when the paddles are deeply 
immersed is ascribed by Barlow to the lessening of the 
shock sustained by the common paddle-wheel when it 
strikes the water. This being the case, the triple wheel of 
Stevens is probably superior to that of Morgan in its effi- 
ciency, while it has the advantage of being far simpler and 
less liable to be put out of order. — a. e. 

*A paddle wheel resembling this has lat ely been constructed by 
Messrs. Seawards. It has been charged by Mr. Morgan as being a co- 
lourable invasion of his patent, and the dispute has been brought into 
the courts of law. 



264 THE STEAM ENGINE. 

(119.) To form an approximate estimate of the limit of 
the present powers of steam navigation, it will be necessary 
to consider the mutual relation of the capacity or tonnage of 
the vessel; the magnitude, weight, and power of the ma- 
chinery; the available stowage for fuel; and the average 
speed attainable in all weathers, as well as the general pur- 
poses to which the vessel is to be appropriated, whether for 
the transport of goods and merchandise, or merely of de- 
spatches and passengers. That portion of the capacity of 
the vessel which is appropriated to the moving power con- 
sists of the space occupied by the machinery and the space 
occupied by the fuel; the magnitude of the latter will 
necessarily depend upon the length of the voyage which the 
vessel must make without receiving a fresh supply of coals 
If the voyage be short, this space may be proportionally 
limited, and a greater portion of room will be left for the 
machinery. If, on the contrary, the voyage be longer, a 
greater stock of coals will be necessary, and a less space will 
remain for the machinery. More powerful vessels, there- 
fore, in proportion to their tonnage, may be used for short 
than for long voyages. 

Taking an average of fifty-one voyages made by the 
Admiralty steamers, from Falmouth to Corfu and back 
during four years ending June, 1834, it was found that the 
average rate of steaming, exclusive of stoppages, was 7i 
miles per hour, taken in a direct line between the places, 
and without allowing for the necessary deviations in the 
course of the vessel. The vessels which performed this 
voyage varied from 350 to 700 tons burthen by measure- 
ment, and were provided with engines varying from 100 
horse to 200 horse power, with stowage for coals varying 
from 80 to 240 tons. The proportion of the power to the 
tonnage varied from 1 horse to 3 tons to 1 horse to 4 tons; 
thus, the Messenger had a power of 200 horses, and mea- 
sured 730 tons; the Flamer had a power of 120 horses, 



PL X 




Fio 69 




Fia 68 







ip 



STEAM NAVIGATION. 265 

and measured 500 tons; the Columbia had 120 horses, and 
measured 360 tons. 

In ^Eneral, it may be assumed that for the shortest class 
of trips, such as those of the Margate steamers, and the 
packets between Liverpool or Holyhead and Dublin, the 
proportion of the power to the tonnage should be that of 1 
horse power to every 2 tons by measure; while for the 
longest voyages the proportion would be reduced to 1 horse 
to 4 tons, voyages of intermediate lengths having every 
variety of intermediate proportion. 

Steamers thus proportioned in their power and tonnage 
may then, on an average of weathers, be expected to make 
7^ miles an hour while steaming, which is equivalent to 174 
miles per day of twenty-four hours. But, in very long 
voyages, it rarely happens that a steamer can work con- 
stantly without interruption. Besides stress of weather, in 
which she must sometimes lie-to, she is liable to occasional 
derangements of her machinery, and more especially of 
her paddles. In almost every long voyage hitherto attempt- 
ed, some time has been lost in occasional repairs of this, 
nature while at sea. We shall perhaps, therefore, for long 
voyages, arrive at a more correct estimate of the daily run 
of a steamer by taking it at 160 miles.* 

By a series of carefully conducted experiments on the 
consumption of coals, under marine boilers and common 
land boilers, which have been lately made at the works of 

* The American reader will hardly be able to refrain from a smile at 
this estimate of Dr. Lardner of the speed of steamboats, founded upon the 
most improved practice of Europe at the close of the year 1835. The 
boats on the Hudson River have for years past averaged a speed of 15 
miles per hour, and the Lexington, which was constructed for a navigation 
part of which is performed in the open ocean, could probably keep up a 
speed of the same amount, except in severe storms. With boats, con- 
structed on the principles of those which navigate Long Island Sound 
and the Chesapeake, we should not fear to assume 12 miles per hour, of, 
upwards of 280 miles per day as their average rate of crossing the 
ocean. — a. e. 

34 



266 THE STEAM ENGINE. 

Mr. Watt, near Birmingham, it has been proved that the 
consumption of fuel under marine boilers is less than under 
land boilers, in the proportion of 2 to 3 very nearly. On 
the other hand, I have ascertained from general observation 
throughout the manufacturing districts in the North of Eng- 
land, that the average consumption of coals under land 
boilers of all powers above the very smallest class is at the 
rate of 15 pounds of coals per horse power per hour. From 
this, result, the accuracy of which may be fully relied upon, 
combined with the result of the experiments just mentioned 
at Soho, we may conclude that the average consumption of 
marine boilers will be at the rate of 10 lbs. of coal per horse 
power per hour. Mr. Field, of the firm of Maudslay and 
Field, in his evidence before a Select Committee of the 
House of Commons on Steam Navigation to India, has 
stated from his observation, and from experiments made at 
different periods, that the consumption is only 8 lbs. per 
horse power per hour. In the evidence of Mr. William 
Morgan, however, before the same committee, the actual 
consumption of fuel on board the Mediterranean packets is 
estimated at 16 cwt. per hour for engines of 200 horse 
power, and Si cwt. for engines of 100 horse power. From 
my own observation, which has been rather extensive both 
with respect to land and marine boilers, I feel assured that 
10 lbs. per hour more nearly represents the practical con- 
sumption than the lower estimate of Mr. Field. We may 
then assume the daily consumption of coal by marine 
boilers, allowing them to work upon an average for 22 
hours, the remainder of the time being left for casual stop- 
pages, at 220 lbs. of coal per horse power, or very nearly 1 
ton for every ten horses' power. In short voyages, where 
there will be no stoppage, the daily consumption will a little 
exceed this; but the distance traversed will be proportionally 
greater. 

When the proportion of the power to the tonnage remains 
unaltered, the speed of the vessel does not materally change. 



STEAM NAVIGATION. 2G7 

We may therefore assume that 10 pounds, of coal per horse 
power will carry a sea-going steamer adapted for- long 
voyages 7% miles direct distance; and therefore to carry her 
100 miles will require 138 pounds, or the T ^th part of a ton 
nearly. Now, the Mediterranean steamers are capahle of 
taking a quantity of fuel at the rate of 1£ tons per horse 
power; hut the proportion of their power to their tonnage 
is greater than that which would probably be adapted for 
longer runs. We shall, therefore, perhaps be warranted in 
assuming that it is practicahle to construct a steamer capable 
of taking 1§ tons of fuel per horse power. At the rate of 
consumption just mentioned, this would be sufficient to 
carry her 2400 miles in average weather; but as an allow- 
ance of fuel must always be made for emergencies, we can- 
not suppose it possible for her to encounter this extreme 
run. Allowing, then, spare fuel to the extent of a quarter 
of a ton per horse power, we should have as an extreme 
limit of a steamer's practicable voyage, without receiving a 
relay of coals, a run of about 2000 miles. 

(120.) This computation is founded upon results obtained 
from the use chiefly of the North of England coal. It has, 
however, been stated in evidence before the select commit- 
tee above mentioned, that the Llangennech coal of Wales 
is considerably more powerful. Captain Wilson, who com- 
manded the Hugh Lindsay steamer in India, has stated that 
this coal is more powerful than Newcastle, in the proportion 
of 9 to 64. * Some of the commanders of the Mediterranean 
packets have likewise stated that the strength of this coal is 
greater than that of Newcastle in the proportion of 16 to 11. t 
So far then as relates to this coal, the above estimate must be 
modified, by reducing the consumption nearly in the propor- 
tion of 3 to 2. 

The class of vessels best fitted for undertaking long voy- 

• Vide Report of Select Committee on Steam Navigation, p. 152. 
f Ibid. p. 7. 



268 THE STEAM ENGINE. 

ages, without relays of coal, would be one from about 800 to 
1000 tons measurement furnished with engines from 200 to 
250 horse power.* Such vessels could take a supply of from 
300 to 400 tons of coals, which being consumed at the rate 
of from 20 to 25 tons per day, would last about fifteen days. 

Applying these results, however, to particular cases, it 
will be necessary to remember that they are average calcu- 
lations, and must be subject to such modifications as the cir- 
cumstances may suggest in the particular instances: thus, if 
a voyage is contemplated under circumstances in which an 
adverse wind generally prevails, less than the average speed 
must be allowed, or, what is the same, a greater consump- 
tion of fuel for a given distance. Against a strong head wind, 
in which a sailing vessel would double-reef her top-sails, 
even a powerful steamer cannot make more than from 2 to 3 
miles an hour, especially if she has a head sea to encounter. 

(121.) In considering the general economy of fuel, it may 
be right to state, that the. results of experience obtained in 
the steam navigation of our channels, and particularly in the 
case of the Post Office packets on the_ Liverpool station, have 
clearly established the fact, that by increasing the ratio of the 
power to the tonnage, an actual saving of fuel in a given dis- 
tance is effected, while at the same time the speed of the ves- 
sel is increased. In the case of the Post Office steamers 
called the Dolphin and the Thetis (Liverpool station,) the 
power has been successively increased, and the speed pro- 
portionably augmented ; but the consumption of fuel per 
voyage between Liverpool and Dublin has been diminished. 
This, at first view, appears inconsistent with the known 
theory of the resistance of solids moving through fluids ; 
since this resistance increases in the same proportion as the 
square of the speed. But this physical principle is founded 

* Engines in steam vessels generally work considerably above their 
nominal power. The power, however, to which we uniformly refer is the 
nominal power, or that power at which they would work with steam of 
the ordinary pressure. 



STEAM NAVIGATION. 2G9 

on the supposition that the immersed part of the floating 
body remains the same. Now I have myself proved by ex- 
periments on canals, that when the speed of the boat is in- 
creased beyond a certain limit, its draught of water is rapid- 
ly diminished; and in the case of a large steam raft con- 
structed upon the river Hudson, it was found that when the 
speed was raised to 20 miles an hour, the draught of water 
was diminished by 7 inches. I have therefore no doubt 
that the increased speed of steamers is attended with a like 
effect ; that, in fact, they rise out of the water ; so that, al- 
though the resistance is increased by reason of their increas- 
ed speed, it is diminished in a still greater proportion by rea- 
son of their diminished immersion. 

Meanwhile, whatever be the cause, it is quite certain that 
the resistance in moving through the water must be dimi- 
nished, because the moving power is always in proportion to 
the quantity of coals consumed, and at the same time in the 
proportion to the resistance overcome. Since, then, the 
quantity of coals consumed in a given distance is diminished 
while the speed is increased, the resistance encountered 
throughout the same distance must be proportionally dimi- 
nished. 

(122.) Increased facility in the extension and application 
of steam navigation is expected to arise from the substitution 
of iron for wood, in the construction of vessels. Hitherto 
iron steamers have been chiefly confined to river navigation; 
but there appears no sufficient reason why their use should 
be thus limited. For sea voyages they offer many advan- 
tages ; they are not half the weight of vessels of equal ton- 
nage constructed of wood ; and, consequently, with the 
same tonnage they will have less draught of water, and' 
therefore less resistance to the propelling power ; or, with 
the same draught of water and the same resistance, they 
will carry a proportionally heavier cargo. The nature of 
their material renders them more stiff and unyielding than 
timber; and they do not suffer that effect which is called hog- 



270 THE STEAM ENGINE. 

ging, which arises from a slight alteration which takes place 
in the figure of a timher vessel in rolling, accompanied by 
an alternate opening and closing of the seams. Iron vessels 
have the further advantage of being more proof against frac- 
ture upon rocks. If a timber vessel strike, a plank is broken, 
and a chasm opened in her many limes greater than the 
point of rock which produces the concussion. If an iron 
vessel strike she will either merely receive a dinge, or be 
pierced by a hole equal in size to the point of rock which 
she encounters. Some examples of the strength of iron ves- 
sels was given by Mr. Macgregor Laird, in his evidence be- 
fore the Committee of the Commons on Steam Navigation, 
among which the following may be mentioned: — An iron 
vessel, called the Alburkah, in one of their experimental 
trials got aground, and lay upon her anchor : in a wooden 
vessel the anchor would probably have pierced her bottom ; 
in this case, however, the bottom was only dinged. An 
iron vessel, built/or the Irish Inland Navigation Company, 
was being towed across Lough Derg in a gale of wind, when 
the towing rope broke, and she was driven upon rocks, on 
which she bumped for a considerable time without any in- 
jury. A woodenivessel would in this case have gone to 
pieces. A further advantage of iron vessels (which in warm 
climates is deserving of consideration) is their greater cool- 
ness and perfect freedom from vermin. 

(123.) The greatest speed which has yet been attained 
upon water by the application of steam has been accomplish- 
ed in the case of a "river steamer of peculiar form, which has 
been constructed upon the river Hudson. This boat, or ra- 
ther raft, consisted of two hollow vessels formed of thin sheet 
iron, somewhat in the shape of spindles or cigars '(from 
wbence a it was calledjhe cigar boat.) In the thickest part 
these floats were eight feet in diameter, tapering towards the 
ends, and about 300 feet long : these floats or buoys, being 
placed parallel to each other, having a distance of more than 
16 feet between them, supported a deck or raft 300 feet 



STEAM NAVIGATION. 271 

long, and 32 feet wide. A paddle wheel 30 feet in diame- 
ter and 16 feet broad revolved between the spindles, impel- 
led by a steam engine placed upon the deck. This vessel 
drew about 30 inches of water, and attained a speed of from 
20 to 25 miles an hour : she ran upon a bank in the river 
Hudson, and was lost. The projecter is now employed in 
constructing another vessel of still larger dimensions. It is 
evident that such a structure is altogether unfitted for sea 
navigation. In the case of a wide navigable river, however, 
such as the Hudson, it will no doubt be attended with the 
advantage of greater expedition. 

(124.) Several projects for the extension of steam naviga- 
tion to voyages of considerable length have lately been en- 
tertained both by the public and by the legislature, and have 
imparted to every attempt to improve steam navigation in- 
creased interest. A committee of the House of Commons 
collected evidence and made a report in the last session in 
favour of an experiment to. establish a line of steam commu- 
nication between Great Britain and India. Two routes have 
been suggested by the committee, each being a continuation 
of the line of Admiralty steam packets already established 
to Malta and the Ionian Isles. One of the routes proposed is 
through Egypt, the Red Sea, and across the Indian Ocean to 
Bombay, or some of the other Presidencies; the other across 
the north part of Syria to the banks of the Euphrates, by that 
river to the Persian Gulf, and from thence to Bombay. 
Each of these routes will be attended with peculiar difficul- 
ties, and in both a long sea voyage will be encountered. 

In the route by the Red Sea, it is proposed to establish 
steamers between Malta and Alexandria (860 miles.) A 
steamer of 400 tons burthen and 100 horse power would 
perform this voyage, upon an average of all weathers inci- 
dent to the situation, in from 5 to 6 days, consuming 10 tons 
of coal per day. But it is probable that it might be found 
more advantageous to establish a higher ratio between the 
power and the tonnage. From Alexandria, the transit might 



272 THE STEAM ENGINE. 

be effected by land across the Isthmus to Suez — a journey of 
from 4 to 5 days — by caravan and camels; or the transit 
might be made either by land or water from Alexandria to 
Cairo, a distance of 173 miles ; and from Cairo to Suez, 93 
miles, across the desert, in about 5 days. At Suez would be 
a station for steamers, and the Red Sea would be traversed in 
3 runs or more. If necessary, stations for coals might be 
established at Cosseir, Judda, Mocha, and finally at Socatra 
— an island immediately beyond the mouth of the Red Sea, 
in the Indian Ocean : the run from Suez to Cosseir'would 
be 300 miles — somewhat more than twice the distance from 
Liverpool to Dublin. From Cosseir to Judda, 450 miles ; 
from Judda to Mocha, 517 miles ; and from Mocha to So- 
catra, 632 miles. It is evident that all this would, without 
difficulty, in the most unfavourable weather, fall within the 
present powers of steam navigation. If the terminus of the 
passage be Bombay, the run from Socatra to Bombay will 
be 1200 miles, which would be, upon an average of weather, 
about 8 days' steaming. The whole passage from Alexan- 
dria to Bombay, allowing 3 days for delay between Suez 
and Bombay, would be 26 days : the time from Bombay to 
Malta would therefore be about 33 days; and adding 14 
days to this for the transit from Malta to England, we should 
have a total of 47 days from London to Bombay, or about 
7 weeks. 

If the terminus proposed were Calcutta, the course from 
Socatra would be 1250 miles south-east to the Maldives, 
where a station for coals would be established. This dis- 
tance would be equal to that from Socatra to Bombay. From 
the Maldives, a run of 400 miles would reach the southern 
point of Ceylon," called the Point de Galle, which is the best 
harbour (Bombay excepted) in British India : from the 
Point de Galle, a run of 600 miles will reach Madras; and 
from Madras to Calcutta would be a run of about 600 miles. 
The voyage from London to Calcutta would be performed 
in about 60 days. 



STEAM NAVIGATION. 273 

At a certain season of the year there exists a powerful 
physical opponent to the transit from India to Suez : from 
the middle of June until the end of September, the south- 
west monsoon blows with unabated force across the Indian 
Ocean, and more particularly between Socatra and Bombay. 
This wind is so violent as to leave it barely possible for the 
most powerful steam packet to make head against it, and the 
voyage could not be accomplished without serious wear and 
tear upon the vessels during these months — if indeed it would 
be practicable at all for any continuance in that season. The 
attention of parliament has therefore been directed to another 
line of communication, not liable to this difficulty : it is pro- 
posed to establish a line of steamers from Bombay through 
the Persian Gulf to the Euphrates. The run from Bombay 
to a place called Muscat, on the southern shore of the Gulf, 
would be 840 miles in a north-west direction, and therefore 
not opposed to the south-west monsoon. From Muscat to 
Bassidore, a point upon the northern coast of the Strait at the 
mouth of the Persian Gulf, would be a run of 255 miles; 
from Bassidore to Bushire, another point on the eastern coast 
of the Persian Gulf, would be a run of 300 miles ; and from 
Bushire to the mouth of the Euphrates, would be 120 miles. 
It is evident that the longest of these runs would offer no 
more difficulty than the passage from Malta to Alexandria. 
From Bussora near the mouth of the Euphrates, to Bir, a 
town upon its left bank near 'Aleppo, would be 1143 miles, 
throughout which there are no physical obstacles to the ri- 
ver navigation which may not be overcome. Some difficul- 
ties arise from the wild and savage character of the tribes 
who occupy its banks. It is, however, thought that by pro- 
per measures, and securing the co-operation of the Pacha of 
E°ypt, any serious obstruction from this cause may be re- 
moved. From Bir, by Aleppo, to Scanderoon, a port upon 
the Mediterranean, opposite Cyprus, is a land journey, said 
to be attended with some difficulty but not of great length; 
and from Scandaroon to Malta is about the same distance as 

35 



274 THE STEAM ENGINE. 

between the latter place and Alexandria. It is calculated 
that the time from London to Bombay by the "Euphrates — 
supposing the passage to be successfully established-^— would 
be a few days shorter than by Egypt and the Red Sea. 

Whichever of these courses may be adopted, it is clear 
that the difficulties, so far as the powers of the steam engine 
are concerned, lie in the one case between Socatra and Bom- 
bay, or between Socatra and the Maldives, and in the other 
case between Bombay and Muscat. Even the run from 
Malta to Alexandria or Scandaroon is liable to objection, 
from the liability of the boiler to deposite and incrustation, 
unless some effectual method be taken to remove this source 
of injury. If, however, the contrivance of Mr. Hall, or of 
Mr. Howard, or any other expedient for a like object, be 
successful, the difficulty will then be limited to the necessary 
supply of coals for so long a voyage. This, however, has 
already been encountered and overcome on four several voy- 
ages by the Hugh Lindsay steamer from Bombay to Suez: 
that vessel encountered a still longer run on these several 
trips, by going, not to Socatra but to Aden, a point on the 
coast of Arabia near the Straits of Babel Mandeb, being a 
run of 1641 miles, which she performed in 10 days and 19 
hours. The entire distance from Bombay to Suez was in 
one case performed in 16 days and 16 hours ; and under the 
most unfavourable circumstances, in 23 days. The average 
was 21 days for each trip. 

(125.) Another projected line of steam communication, 
which offers circumstances of equal interst to the people of 
these countries and the United States, is that which is pro- 
posed to be established between London and New York. On 
the completion of the London and Liverpool railroad, Dub- 
lin will be connected with London, by a continuous line of 
steam transport. It is proposed to continue this line by a 
railroad from Dublin to some point on the western coast of 
Ireland; among others, the harbour of Valektia has been 
mentioned. The nearest point of the western continent is 



STEAM NAVIGATION. 275 

St. John's, Newfoundland, the distance of which from Va- 
leria is 1900 miles ; the distance from St. John's to New 
,York is about 1200 miles, Halifax (Nova Scotia) being a 
convenient intermediate station. The distance from Valen- 
tia to St. John's comes very near the point which we have 
already assigned as the probable present limit of steam navi- 
gation. The Atlantic Ocean also ofiers a formidable oppo- 
nent in the westerly winds which almost constantly prevail 
in it. These winds are, in fact, the reaction of the trades, 
which blow near the equator in a contrary direction, and are 
produced by those portions of the equatorial atmosphere 
which,, rushing down the northern latitudes, carry with them 
the velocity from west to east proper to the equator. Be- 
sides this difficulty, St. John's and Halifax are both inacces- 
sible, by reason of the climate, during certain months of the 
^ year. Should these causes prevent this project from being 
realized, another course may be adopted. We may proceed 
from the southern point of Ireland or England to the Azores, 
a distance of about 1800 miles: from the Azores to New 
York would be a distance of about 2000 miles, or from the 
Azores to St. John's would be 1600 miles.* 

(k) While the inhabitants of Great Britain are discussing 

* A treatise on the Steam Engine is not the place to enter into dis- 
cussion on the causes of the several constant, periodic, and prevailing 
winds, otherwise we should feel it our duty to correct the opinion adopt- 
ed by Dr. Lardner from the older authorities, in relation to the course 
of the westerly winds. 1'hese winds are, in the South Atlantic, and in 
both South and North Pacific, constant winds. In the North Atlantic 
between the latitudes, of 35° and 45°, and, therefore, in the track of the 
vessels which navigate between the United States and Great Britain, they 
are the most frequent prevailing winds, except in the months of April 
and October. They are certainly not the reaction of the trade winds, 
which is in a well known zone, to the south of the region in which these 
westerly winds prevail, under the name of the Horse latitudes of our na- 
vigations, and the Grassy sea of the Spaniards. Those who wish to study 
the true theoiy of these winds will find it in Daniell's learned and inge- 
nious work, " On Atmospheric Phenomena," or in the analysis' of that 
work in the American Quarterly Review. 



276 THE STEAM ENGINE. 

the project of the communication with New York, by means 
of the stations described by Dr. Lardner, those of the United 
States appear to be seriously occupied in carrying into effecjj 
a direct communication from New York to Liverpool. ' At 
the speed which has been given to the American steam boats, 
this presents no greater difficulties than the voyage from the 
Azores to New York, would, to. one having the speed of no 
more than 7i miles per hour. As this attempt is beyond the 
limit of individual enterprise, there is, at the present mo- 
ment, an application before the Legislature of the State of 
New York for a charter to carry this project into effect. It 
will be difficult to estimate the results of this enterprise, 
which will bring the old and new world within 12 or 15 
days voyage of each other. — a. e. # 

* Dr. Lardner appears purposely to have omitted any detail of the his- 
tory of Steam Navigation. It would be an invidious task on the part 
of a mere editor to attempt to supply what he has thought proper to avoid. 
We therefore merely refer to this subject for the purpose of expressing 
the hope, that tins silence is an earnest that the writers of Europe are 
about to abandon the claims they have set up for their countrymen to the 
merit of introducing the successful practice of Steam navigation, and that 
* the respective services of Fitch, Evans, Fulton, and the elder Stevens 
will soon be universally acknowledged. — a. e. 



277 
CHAPTER XII. 

GENERAL ECONOMY OF STEAM POWER. 

Mechanical efficacy of steam — proportional to the quantity of water eva- 
porated, and to the fuel consumed — Independent of the pressure. — Its 
mechanical efficacy by condensation alone. — By condensation and ex- 
pansion combined — by direct pressure and expansion — by direct pres- 
sure and condensation — by direct pressure, condensation, and expan- 
sion. — The power of engines. — The duty of engines. — Meaning of horse 
power. — To compute the power of an engine. — Of the power of boil- 
ers. — The structure of the grate bars. — Quantity of water* and steam 
room. — Fire surface and flue surface. — Dimensions of steam pipes. — 
Velocity of piston. — Economy of fuel. — Cornish duty reports. 

(130.) Having explained in the preceding chapters the 
most important circumstances connected with the principal 
varieties of steam engines, it remains now to explain some 
matters of detail connected with the power, efficiency, and 
economy of these machines, which, though perhaps less 
striking and attractive than the subjects which have hitherto 
engaged us, are still not undeserving of attention. 

It has been shown in the first chapter, that water exposed 
to the ordinary atmospheric pressure (the amount of which 
may be expressed by a column of 30 inches of mercury) will 
pass from the liquid into the vaporous state when it arrives 
at the temperature of 212°; and the vapour thus produced 
from it will have an elastic force equal to that of the atmos- 
phere. If the water, however, to which heat is applied, be 
submitted to a greater or less pressure than that of the at- 
mosphere, it will boil at a greater or less temperature, and 
will always produce steam of an elastic force equal to the 
pressure under which it boils. Now it is a fact as remark- 
able as it is important, that to convert a given weight of wa- 
ter into vapour will require the same quantity of heat, under 
whatever pressure, and at whatever temperature the water 
may boil. Let us suppose a tube, the base of which is equal 



278 THE STEAM ENGINE. 

to a square foot, in which a piston fits air-tight and steam- 
tight. Immediately under the piston, let a cubic inch of 
water be placed, which will be spread in a thin layer over 
the bottom of the tube. Let the piston be counterbalanced 
by a weight (acting over a pulley) which will be equivalent 
to the weight of the piston, so that it shall be free to ascend 
by the application of any pressure below it. Now let the 
flame of a lamp be applied at the bottom of the tube : the 
water under the piston being affected by no pressure from 
above, except that of the atmosphere acting upon the piston, 
will boil at the temperature of 212°, and by the continued 
application of the lamp it will at length be converted into 
steam. The steam into which the cubic inch of water is 
converted will expand into the magnitude of a cubic foot, 
exerting an elastic force equal to the atmospheric pressure; 
consequently the piston will be raised one foot above its 
first position in the tube, and the cubic foot beneath it will 
be completely filled with steam. Let us suppose, that to 
produce this effect required the lamp to be applied to the 
tube for the space of fifteen minutes. 

The water being again supposed at its original tempera? 
ture, and the piston in its first position, let a weight be 
placed upon the piston equal to the pressure of the atmos- 
phere, so that the water beneath the piston will be pressed 
down by double the atmospheric pressure. If the lamp be 
once more applied, the water will, as before, be converted 
into vapour ; but the piston will now be raised to the height 
of only six inches* from the bottom, the steam expanding 
into only half its former bulk. The temperature at which 

* Strictly speaking 1 , the height to which the piston would be raised 
would not diminish in so great a proportion as the pressure is increased, 
because the increase of pressure being necessarily accompanied by an 
increase of temperature, a corresponding expansion would be produced. 
Therefore there will be a slight increase in the total mechanical effect of 
the steam. The difference, however, is not very important in practice, 
and it is usual to consider the density of steam as proportional to the 
pressure. 



MECHANICAL FORCE OE STEAM. 279 

the water would commence to be converted into vapour, in- 
stead of being 212°, would be 250°; but the time elapsed 
between the moment of the first application of the lamp, and 
the complete conversion of the water into steam, will still 
be fifteen minutes. 

Again, if the piston be loaded with a weight equal to 
double the atmospheric pressure, the water will be pressed 
down by the force of three atmospheres. If the lamp be 
applied as before, the water would be converted into steam 
in the same time; but the piston will now be raised only 
four inches above its first position, and the steam will con- 
sequently be three times as dense as when the piston was 
pressed down only by the atmosphere. 

From these and similar experiments we infer: — 

First, That the elastic pressure of steam is equal to the 
mechanical pressure under which the water producing the 
steam has been boiled. 

Secondly, That the bulk which steam fills is diminished 
in the same proportion as the pressure of the steam is in- 
creased; or, in other words, that the density of steam is 
always in the same proportion as its pressure. 

Thirdly, That the same quantity of heat is sufficient to 
convert the same weight of water into steam, whatever be 
the pressure under which the water is boiled, or whatever 
be the density and pressure of the steam produced. 

Fourthly, That the same quantity of water being con- 
verted into steam, produces the same mechanical effect, 
whatever be the pressure or the density of the steam. Thus, 
in the first case, the weight of one atmosphere was raised a 
foot high; in the second case, the weight of two atmospheres 
was raised through half a fool; and, in the third case, the 
weight of three atmospheres was raised through the third of 
a foot; the weight raised being in every case increased in 
the same proportion as the height through which it is ele- 
vated is diminished. Every increase of the weight is, 
therefore, compensated by a proportionate diminution of the 



280 „ THE STEAM ENGINE. 

height through which it is raised, and the mechanical effect 
is consequently the same. 

Fifthly, That the same quantity of heat or fuel is neces- 
sary and sufficient to produce the same mechanical effect, 
whatever be the pressure of the steam which it produces. 

If steam be used to raise a piston against the atmospheric 
pressure only, although a definite physical force will be 
exerted by it, and a mechanical effect produced, yet under 
such circumstances it will exert no directly useful efficiency; 
but after the piston has been raised, and the tube beneath it 
filled with steam balancing the atmosphere above it, a useful 
effect to the same amount may be obtained by cooling the 
tube, and thereby reconverting the steam into water. The 
piston will thus be urged downwards by the unresisted force 
of the atmosphere, and any chain or rod attached to it will 
be drawn downwards with a corresponding force. If the 
area of the piston be, as already supposed, equal to the mag- 
nitude of one square foot, the atmospheric pressure upon it, 
being 15 pounds for each square inch, will amount to 144 
times 15 pounds, or 2160 pounds. By drawing down a 
chain or rope acting over a pulley, the piston would in its 
descent (omitting the consideration of friction, &c.) raise a 
weight of 2160 pounds a foot high. Since 2160 pounds are 
nearly equal to one ton, it may, for the sake of round num- 
bers be stated thus: — 

" Ji cubic inch of water, being converted into steam, 
will, by the condensation of that, steam, raise a ton 
weight a foot high." Such is the way in which the force 
of steam is rendered practically available in the atmospheric 
engine. 

(131.) The method by which steam is used in the single- 
acting steam engine of Watt is, in all respects, similar, ex- 
cept that the piston, instead of being urged downwards by 
the force of the atmosphere, is pressed by steam of a force 
equal to the atmospheric pressure. It is evident, however, 
that this does not alter the mechanical result. 



EFFECT OF EXPANSION. 281 

We have stated that a considerable increase of power, 
from a given quantity of steam, was produced by cutting off 
the steam after the piston, had made a part of its descent, 
and allowing the remainder of the descent to be produced 
by the expansive force of the steam already admitted. We 
shall now more fully explain the principle on which this 
increase of power depends. 

Let a b {Jig. 69.,) as before, represent a tube, the bottom 
of which is equal to a square foot, and let p be a piston in it, 
resting upon a cubic inch of water spread over the bottom ; 
and let w be an empty vessel, the weight of which exactly 
counterpoises the piston. By the application of the lamp, 
the water will be converted into steam of the atmospheric 
pressure, and the piston will be raised from p to p', through 
the height of one foot, the space in the tube beneath it being 
filled with steam, and the vessel w will have descended 
through one foot. Let half- a ton of water be now poured 
into the vessel w ; its weight will draw the piston p' up- 
wards, so that the steam below it will expand into a larger 
space. When the piston p' was only balanced by the empty 
vessel w, it was pressed downwards by the whole weight 
of the atmosphere above, which amounts to about one ton: 
now, however, half of this pressure is balanced by the half 
ton of water poured into the vessel w ; consequently the 
effective downward pressure on the piston p' will be only 
half a ton, or half its former amount. The piston will there- 
fore rise, until the pressure of the steam below it is diminish- 
ed to the same extent. By what has been already explained, 
this will take place when the steam is allowed to expand 
into double its former bulk ; consequently, when the piston 
has risen to p", one foot higher, or two feet from the bottom 
of the tube, the steam will then exactly balance the down- 
ward pressure on the piston, and the latter will remain sta- 
tionary ; the vessel w, with the half ton of water it contains, 
will have descended one foot lower, or two feet below its first 
position. Let the steam now be cooled and reconverted into 

36 



282 THE STEAM ENGINE. 

water, and at the same time let another half ton of water be 
supplied to the vessel w ; the pressure below the piston being 
entirely removed, the atmospheric pressure will act above it 
with undiminished force; and this force, amounting to one 
ton, will draw up the vessel w, with its contents. When the 
piston descends, as it will do, to the bottom of the tube, the 
ton of water contained in the vessel w will be raised through 
two perpendicular feet.* 

Now, in this process it will be observed that the quantity 
of steam consumed is not more than in the former case, viz. 
the vapour produced by boiling one cubic inch of water. 
Let us consider, however, the mechanical effect which has re- 
sulted from it; half a ton of water has been allowed to descend 
through one foot, while a ton has been raised through two 
feet: deducting the force lost by the descent of half a ton 
through one foot from the force obtained by the ascent of 
one ton through the two feet, we obtain for the whole me- 
chanical effect one ton and a half raised through one foot; 
for it is evident that half a ton has been raised from the 
lowest point to which the vessel w descended one foot above 
that point, and one ton has been raised through the other 
foot, which is equivalent to one ton and a half through one 
foot. 

Comparing this with the effect produced in the first case, 
where the steam Was condensed without causing its expan- 
sion, it will be evident that there is an increase of 50 per 
cent, upon the whole mechanical effect produced. 

But this is not the limit of the increase of power by ex- 
pansion. Instead of condensing the steam when the piston 
had arrived at p", let a further quantity of water amounting 
to one sixth of a ton be poured into the vessel w, in addi- 
tion to the half ton which it previously contained ; the ef- 

* Strictly speaking, the quantity of water supposed in these cases to 
be placed in the vessel w would just balance the atmospheric pressure. 
A slight preponderance must therefore be given to the piston, to produce 
the motion. 



EFFECT OF EXPANSION. 283 

fective pressure on the piston p", being only half a ton, will 
be overbalanced by the preponderating weight in the vessel 
w, and the piston will consequently ascend. It will become 
stationary when the steam by expansion loses a quantity of 
force equal to the additional weight which the vessel w has 
received: now, that -vessel, having successively received a 
half and a sixth of a ton will contain two thirds of a ton; 
consequently the effective downward pressure on the piston 
will be only a third of a ton, and the steam to balance this 
must, expand into three limes the space it occupied when 
equal to the atmospheric pressure. It must therefore ascend 
to p'", three feet above the bottom of the tube. If the steam 
in the tube be now condensed, and at the same time one 
third of a ton of water be supplied to the vessel w, so as to 
make its total contents amount to one ton, the piston will 
descend, being urged downwards by the unresisted atmo- 
spheric pressure, and the ton of water contained in the ves- 
sel w will be raised through three perpendicular feet. 

In this case, as in the former, the total quantity of steam 
consumed is that of one cubic inch of water; but the me- 
chanical effect it produces is still further increased. To cal- 
culate its amount, we must consider that half a ton of water 
has fallen through two feet, which is equivalent to a ton 
falling through one foot, besides which the sixth part of a 
ton has fallen through one foot. The total loss, therefore, 
by the fall of water has been one ton and one sixth through 
one foot, while the force gained by the ascent of water has 
been one ton raised through three feet, which is equivalent 
to three tons through one foot. If, then, from three tons 
we deduct one and one sixth, the remainder will be one ton 
and five sixths raised through one foot ; this effect being 
above SO per cent, more than that which is produced in the 
first case, where the steam was not allowed to expand. 

To carry the inquiry one step further: Let us suppose 
that, upon the arrival of the piston at p'", a further addition 
of water to the amount of one twelfth of a ton be added to 



284 THE STEAM ENGINE. 

it: this, with the water it already contained, would make 
the to.tal contents three fourths of a ton ; consequently, the 
effective pressure upon the piston would now be reduced to 
one fourth of the atmospheric pressure. The atmospheric 
steam would balance this when expanded into four times its 
original volume : consequently, the piston would come to a 
state of rest at p"", four feet above the bottom of the tube, 
and the vessel w would consequently have descended through 
four perpendicular feet. If the steam in the tube be now 
condensed as in the former cases, and at the same time a 
quarter of a ton of water be added to the vessel w, the pis- 
Ion will descend to the bottom of the tube, and the ton of 
water in the vessel w will be raised through four perpendi- 
cular feet To estimate the mechanical effect thus produced, 
we have, as before, to deduct the total force lost by the fall 
of water from the force gained by its elevation : the water 
has fallen in three distinct portions: first, half a ton has fallen 
through three perpendicular feet, which is equivalent to one 
ton and a half through one foot ; secondly, one sixth of a 
ton has fallen through two perpendicular feet, which is 
equivalent to one third of a ton through one foot; and 
thirdly, one twelfth of a ton has fallen through one foot: 
these added together will be equivalent to one ton and 
eleven twelfths through one foot. One ton has been raised 
through four feet, which is equivalent to four tons through 
one foot: deducting from this the force lost by the descent, 
the surplus gained will be two tons and one twelfth through 
one foot, being about 108 per cent, more than the force re- 
sulting from the condensation of steam without expansion. 

To the increase of mechanical effect to be produced in this 
way, there is no theoretical limit. According to the man- 
ner in which we have here explained it, to produce the 
greatest possible effect by a given extent of expansion, it 
would be necessary to supply the water or other counter- 
poise to the vessel w, not in separate masses, as we have 



EXPANSIVE FOKCE OF STEAM. 285 

here supposed, but continuously, so as to produce a regular 
motion of the piston upwards. 

Such is the principle on which the advantages of the ex- 
pansive engine of Watt and Hornblower depend, explained 
so far as it can be without the aid of the language and rea- 
soning of analysis.* 

(132.) We have here, however, only considered the me- 
chanical effect produced by the condensation of steam. Let 
us now examine its direct action. 

Let the piston p be supposed to be connected by a rod 
with a load or resistance which it is intended to raise, and 
let the load placed upon it be supposed to amount to one ton, 
the total pressure on the piston will then be two tons; one 
due to the atmospheric pressure, and the other to the amount 
of the load. Upon applying heat to the water, steam will 
be produced; and when the water has been completely eva- 
porated, the piston will rise to the height of six inches from 
the bottom of the tube. The total mechanical effect thus 
produced will be one ton weight raised through six perpen- 
dicular inches, which is equivalent to half a ton raised 
through one foot. 

Again, let the load upon the piston be two tons; this will 
produce a total pressure upon the water below it amounting 
to three tons, including the atmospheric pressure. The 
water, when converted into vapour under this pressure, 
will raise the piston and its load through four perpendicular 
inches: the useful mechanical effect will then be two tons 
raised through the third of a foot, which is equivalent to 
two thirds of a ton raised one foot. In the same manner, 
if the piston were loaded with three tons, the mechanical 
effect would be equivalent to three fourths of a ton raised 
through one foot, and so on. 

* A strict investigation of this important property, as well as of the 
other consequences of the quality of expansion, would require more ab- 
struse mathematical processes than would be consistent with the nature 
of this work. 



286 THE STEAM ENGINE. 

It appears therefore from this reasoning, that when the 
direct force of steam of greater pressure than the atmosphere 
is used without condensation, the total mechanical effect is 
always less than that produced by the condensation of atmo- 
spheric steam without expansion; but that the greater the pres- 
sure under which the steam is produced, the less will be the 
difference between these effects. In general, the proportion 
of the mechanical effect of high pressure steam to the effect 
produced by the condensation of atmospheric steam, will be 
as the number of atmospheres expressing the pressure of the 
steam to^ the same number increased by one. Thus, if 
steam be produced under the pressure of six atmospheres, 
the proportion of its effect to that of the condensation of at- 
mospheric steam will be as six to seven. 

(133.) Another method of applying the power of steam 
mechanically is, to combine its direct action with condensa- 
tion but without expansion. 

The piston being, as before, loaded with one ton, the eva- 
poration of the water will raise it through six perpendicular 
inches, and the result so far will be equivalent to a ton 
raised half a foot; but if the piston rod be supposed also to 
act by a chain or cord over a wheel, so as to pull a weight 
up, the steam which has just raised the ton weight through six 
inches, may be condensed, and the piston will descend with 
a force of one ton into the vacuum thus produced, and ano- 
ther ton may be thus raised through half a foot. The total 
mechanical power thus yielded by the steam, adding to its 
direct action its effect by condensation, will then be one ton 
raised through one foot, being an effect exactly equal to that 
obtained by the condensation of atmospheric steam. 

If the piston be loaded with two tons, its direct action 
will, as we have shown, raise these two tons through four 
inches, which is equivalent to two thirds of a ton raised a 
foot. By condensing this steam a ton weight may be raised 
in the same manner, by the descent of the piston through a 



EXPANSION AND CONDENSATION. 287 

third of a foot, which is equivalent to the third of a ton 
raised through one foot. 

By pursuing like reasoning, it will appear that, if the 
direct force of high-pressure steam be combined with the 
indirect force produced by its condensation, the total me- 
chanical effect will be precisely equal to the mechanical 
effect by the mere condensation of atmospheric steam. 

• (134.) In applying the principle of expansion to the direct 
action of high pressure steam, advantages are gained analo- 
gous to those already explained with reference to the method 
of condensation. 

Let the piston be supposed to be loaded with three tons: 
the evaporation of the water beneath it will raise this weight, 
including the atmospheric pressure, through three perpendi- 
cular inches. Let one ton be now removed, and the remain- 
ing two tons will be raised, by the expansion of the steam, 
through another perpendicular inch. Let the second ton 
be now removed, and the piston loaded with the remaining 
ton will rise, by the expansion of the steam, to the height 
of six inches from the bottom. These consequences follow 
immediately from the principle that steam will expand in 
proportion as the pressure upon it is diminished, observing 
that in this case the atmospheric pressure, amounting to one 
ton, must always be added to the load. In this process 
three separate effects are produced: one ton is raised through 
three inches, which is equivalent to a quarter of a ton raised 
through one foot; another ton is raised through four inches, 
which is equivalent to a third of a ton through a foot, and 
the third ton is raised through six inches, which is equivalent 
to half a ton raised through a foot. The total of these effects 
amounts to one and one-twelfth of a ton raised through one 
foot, while the same load, raised by the high pressure steam 
without expansion, would be equivalent to only half a ton 
raised through one foot. 

Again, let the load placed upon the piston be five tons: 
the evaporation of the water will raise this through the sixth 
part of a foot; if one ton be now removed, the other four 



288 THE STEAM ENGINE. 

tons will be raised to a height above the bottom of the tube 
equal to a fifth part of a foot ;.- another ton being removed, 
the remaining three will be raised to a height from the bot- 
tom equal to a fourth of a foot; and so on, the last ton being 
raised' through half a foot. To estimate the total mechanical 
effect thus produced, we are to consider that the several tons 
raised from their first position are raised through the sixth, 
fifth, fourth, third, and half of a perpendicular foot, giving a 
total effect equal to the sixth, fifth, fourth, third, and half of 
a ton severally raised through one foot; these, therefore, 
added together, will give a total of nineteen twentieths of a 
ton raised through one foot. 

In general, the expansive force applied to the direct action 
of high-pressure steam, therefore, will increase its effect ac- 
cording to the same law, and subject to the same principles 
as were shown with respect to the method of condensation 
accompanied with expansion. 

The expansive action of high pressure steam may be ac- 
companied with condensation, so as considerably to increase 
the mechanical effect produced; for, after the weights with 
which the piston is loaded have been successively raised to 
the extent permitted by the elastic force of the steam, and 
are removed from the piston, the steam will expand until it 
balances the atmospheric pressure. It may afterwards be 
made further to expand, by adding weights to the counter- 
poise w in the manner already explained; and, the steam 
being subsequently condensed, all the effects will be pro- 
duced upon the descent of the piston which we have before 
noticed. It is evident that by this means the mechanical 
effect admits of very considerable increase. 

(135.) We have hitherto considered the piston to be re- 
sisted by the atmospheric pressure above it; but, as is shown 
in the preceding chapters, in the modern steam engines, the 
atmosphere is expelled from the interior of the machine by 
allowing the steam to pass freely through all its cavities in 
the first instance, and to escape at some convenient aperture, 
which, opening outwards, will effectually prevent the subse- 



EXPANSIVE FOTCCE OF STEAM. 289 

quent re-admission of air. The piston rod and other parts 
which pass from the external atmosphere to the interior of 
the machine, are likewise so constructed and so supplied 
with oil or other lubricating matter that neither the escape 
of steam nor the entrance of air is permitted. We are there- 
fore now to consider the effect of the action of steam against 
the piston p, when subjected to a resistance which may be 
less in amount, to any extent, than the atmospheric pres- 
sure. 

In such machines the steam always acts both directly by 
its power, and indirectly by its condensation. In calculating- 
its effects, excluding friction, &c., we have therefore only 
to estimate its total force upon the piston, „and to deduct 
the force of the uncondensed vapour which will resist the 
motion of the piston. 

Supposing, then, the total force exerted upon the piston, 
after deducting the resistance from the uncondensed vapour, 
to be one ton, and the length of the cylinder to be one fopt, 
each motion of the piston from end to end of the cylinder 
will produce a mechanical force equivalent to a to-'» weight 
raised one foot high. If in this case the magnitude of the 
piston be equivalent to one square foot, the pressure of the 
steam will be equal to that of the atmosphere, and the quan- 
tity of water in the form of steam which the cylinder will 
contain will be a cubic inch, while the quantity of steam in 
it will be a cubic foot. In proportion as the area of the pis- 
ton is enlarged the pressure of the steam will be diminished, 
if the moving force is required to remain the same ; but 
with every diminution of pressure the density of the steam 
will be diminished in the same proportion, and the cylinder 
will still contain the same quantity of water in the form of 
vapour. In this way steam may be used, as a mechanical 
agent, with a pressure to almost any extent less than that of 
the atmosphere, and aUemperatures considerably lower than 
212°. To obtain the same mechanical force, it is only ne- 

37 



290 THE STEAM ENGINE. 

cessary to enlarge the piston in the same proportion as the 
pressure of the steam is diminished. 

By a due attention to this circumstance, the expansive 
power of steam, both in its direct action and by condensa- 
tion, may be used with very much increased advantage ; and 
such is the principle on which the benefits derived from 
Woolf's contrivances depend. If steam of a high pressure, 
say of three or four atmospheres, be admitted to the piston, 
and allowed to impel it through a very small portion of the 
descent, it may then be cut off and its expansion may be al- 
lowed to act upon the piston until the pressure of the steam 
is diminished considerably below the atmospheric pressure ; 
the steam may then be condensed and a vacuum produced, 
and the process repeated. 

In the double-acting engines, commonly used in manu- 
factures and in navigation, and still more in the high-pres- 
sure engines used for locomotion, the advantageous applica- 
tion of the principle of expansion appears to have been 
hitherto attended with difficulties ; for, notwithstanding the 
benefits which unquestionably attend it in the eeonomy of 
fuel, it has -svot been generally resorted to. To derive from, 
this principle foil advantage, it would be necessary that the 
varying power of the expanding steam should encounter a 
corresponding, or a nearly corresponding, variation in the 
resistance : this requisite may be attained, in engines applied 
to the purpose of raising water, by many obvious expedients; 
but when they have, as in manufactures, to encounter a near- 
ly uniform resistance, or, in navigation and locomotion, a 
very irregular resistance, the due application of expansion is 
difficult, if indeed it be practicable. 

We have seen that the mechanical effect produced by 
steam when the principle of expansion is not used, is always 
proportional to the quantity of water contained in the steam, 
and is likewise in the same proportion so long as a given 
degree of expansion is used. It is apparent, therefore, that 
the mechanical power which is or ought to be exerted by an 



HOUSE POWER OF ENGINES. 291 

engine is in the direct proportion of the quantity of water 
evaporated. It has also been shown that the quantity of wa- 
ter evaporated, whatever be the pressure of the steam, will 
be in the direct proportion of the quantity of heat received 
from the fuel, and therefore in the direct proportion of the 
quantity of fuel itself, so long as the same proportion of its 
heat is imparted to the water. 

(136.) The power of an engine is a term which has been 
used to express the rate at which it is able to raise a given 
load, or overcome a given resistance. The duty of an en- 
gine is another term, which has been adopted to express the 
load which may be raised a given perpendicular height, by 
the combustion of a given quantity of fuel. 

When steam engines were first introduced, they were com- 
monly applied to work pumps or mills which had been pre- 
viously wrought by horses. . It was, therefore, convenient, 
and indeed necessary, in the first instance, to be able to ex- 
press the performance of these machines by reference to the 
effects of animal power, to which manufacturers, miners, and 
others, had been long accustomed. When an engine, there- 
fore, was capable of performing the same work in a given 
time, as any given number of horses of average strength 
usually performed, it was said to be an engine of so many 
horses' power. This term was long used with much vague- 
ness and uncertainty : at length, as the use of steam engines 
became more extended, it was apparent that confusion and 
inconvenience would ensue, if some fixed and definite mean- 
ing were not assigned to it, so that the engineers and others 
should clearly understand each other in expressing the pow- 
ers of these machines. The term horsepower had so long 
been in use, that it was obviously convenient to retain it. It 
was only necessary to agree upon some standard by which 
it might be defined. The performance of a horse of average 
strength, working for eight hours a day, was, therefore, se- 
lected as a standard or unit of steam-engine power. Smeaton 
estimated the amount of mechanical effect which the animal 



292 THE STEAM ENGINE. 

could produce at 22,916 pounds, raised one foot per. minute; 
Desaguiliers makes it 27,500 pounds, raised through the 
same height. Messrs. Bolton and Watt caused experiments 
to be made with the strong horses used in the breweries in 
London ; and from the result of these they assigned 33,000 
pounds raised one foot per minute, as the value of a horse's 
power : this is, accordingly, the estimate now generally 
adopted ; and, when an engine is said to be of so many 
horses' power, it is meant that, when in good working order 
and properly managed, it is capable of overcoming a resist- 
ance equivalent to so many times 33,000 pounds raised one 
foot per minute. Thus, an engine of ten-horse power 
would be capable of raising 330,000 pounds one foot per 
minute. 

As the same quantity of water converted into steam will 
always produce the same mechanical effect, whatever be the 
density of the steam produced from it, and at whatever rate 
the evaporation may proceed, it is evident that the power of 
a steam engine VqH depend on two circumstances : first, the 
rate at which the boiler with its appendages is capable of 
evaporating water; and, secondly, the rate at which the en- 
gine is capable of consuming the steam by its work. We 
shall consider these two circumstances separately. ■ 

The rate at which the boiler produces steam will depend 
upon the rate at which heat can be transmitted from the fire 
to the water which it contains. Now this heat is transmitted 
in two ways: either by the direct action of the fire radiating 
heat against the surface of the boiler; or by the flatne and 
heated air which escapes from the fire, passing through the 
flues, as already explained. The surface of the boiler ex- 
posed to the direct radiation of the fire is technically called 
fire surface; and that which takes heat from the flame and 
air, on its way to the chimney, is called fine surface. Of 
these the most efficient in the generation of steam is the for- 
mer. In stationary boilers, used for condensing engines, 
where magnitude and weight are matters of little importance, 



HOUSE POWER OF ENGINES. 293 

it has been found that the greatest effect has been produced 
in general by allowing four and a half square feet of fire sur- 
face, and four and a half square feet of flue surface, for every 
horse power. By means of this quantity of fire and flue 
surface, a cubic foot of water per hour may be evaporated. 

It has been already shown that the total power exerted by 
a cubic inch of water, converted into steam, will be equiva- 
lent to 2160 pounds raised one foot. A cubic foot of water 
consists of 1728 cubic inches, and the power produced by 
its evaporation will therefore be found by multiplying 216 
by' 1728; the product, 3,732,480, expresses the number of 
pounds' weight which the evaporation of a cubic foot of wa- 
ter would raise one foot high, supposing that its entire me- 
chanical force were rendered available: but to suppose this 
in practice, would be to suppose the machine, through the 
medium of which it is worked, moved without any power 
being expended upon its own parts. It would be, in fact, 
supposing all its moving parts to be free from friction and 
other causes of resistance. To form a practical estimate, 
then, of the real quantity of available mechanical power ob- 
tained- from the evaporation of a given quantity of water, it 
will be necessary to inquire what quantity of this power is 
intercepted by the engine through which it is transmitted. 
In different forms of steam engine — indeed, we may say in 
every individual steam engine — the amount thus lost is dif- 
ferent; nevertheless, an approximate estimate may be ob- 
tained, sufficiently exact to form the basis of a general con- 
clusion. 

Let us consider, then, severally, the means by which me- 
chanical power is intercepted by the engine. 

First, The steam must flow from the boiler into the cy- 
linder to work the piston; it passes necessarily through pipes 
more or less contracted, and is, therefore, subject to friction 
as well as cooling in its passage. 

Second, Force is lost by the radiation of heat from the 
cylinder and its appendages. 



294 THE STEAM ENGINE. 

Third, The friction of the piston in the cylinder must be 
overcome. 

Fourth, Loss of steam takes place by leakage. 

Fifth, Force is expended in expelling the steam after 
having worked the piston. 

Sixth, Force is required to open and close the several 
valves, to pump up the water for condensation, and to over- 
come the friction of the various axes. 

Seventh, Force is expended upon working the air-pump. 

In engines which do not condense the steam, and which, 
therefore, work with steam of high pressure, some of these 
sources of waste are absent, but others are of increased 
amount. If we suppose the total effective force of the water 
evaporated per hour in the boiler to be expressed by 1000, 
it is calculated that the waste in a high-pressure engine will 
be expressed by the number 392; or, in other words, taking 
the whole undiminished force obtained by evaporation as 
expressed by 10, very nearly 4 of these parts will be con- 
sumed in moving the engine, and the other 6 only will be 
available. 

In a single-acting engine which condenses the steam, tak- 
ing, as before, 1000 to express, the total mechanical power of 
the water evaporated in the boiler, 402 will express the part 
of this consumed in moving the engine, and 598, therefore, 
will express the portion of the power practically available; 
or, taking round numbers, we shall have the same result as 
in the non-condensing engine, viz. the whole force of the 
water evaporated being expressed by 10, 4 will express the 
waste, and 6 the available part. 

In a double acting engine the available part of the power 
bears a somewhat greater proportion to the whole. Taking, 
as before, 10C0 to express the whole force of the water 
evaporated, 36S will express the proportion of that force ex- 
pended on the engine, and 632 the proportion which is 
available for work. 

In general, then, taking round numbers, we may consider 



HORSE POWER OP ENGINES. 295 

that the mechanical force of four tenths of the water evapo- 
rated in the boiler is intercepted by the engine, and the 
olher six tenths are available as a moving force. In this 
calculation, however, the resistance produced in the con- 
densing engine by the uncondensed steam is not taken into 
account: the amount of this force will depend upon the 
temperature at which the water is maintained in the con- 
denser. If this water be kept at the temperature of 120°, 
the vapour arising from it will have a pressure expressed by 
three inches seven tenths of mercury ; if we suppose the 
pressure of steam in the boiler to be measured by 37 inches 
of mercury, then the resistance from the uncondensed 
steam will amount to one tenth of the whole power of 
the boiler ; this, added to the four tenths already accounted 
for, would show a waste amounting to half the whole 
power of the boiler, and consequently only half the water 
evaporated would be available as a moving power. 

If the temperature of the condenser be kept down to 
100°, then the pressure of uncondensed steam will be ex- 
pressed by two inches of mercury, and the loss of power 
consequent upon it would amount to a proportionally less 
fraction of the whole power. 

The following example will illustrate the method of esti- 
mating the effective power of an engine. 

In a double-acting engine, in good working condition, the 
total power of steam in the boiler being expressed by 1000, 
the proportion intercepted by the engine, exclusive of the 
resistance of the uncondensed steam, will be 36S, and the 
effective part 632. Now, suppose the pressure of steam in 
the boiler to be measured by a column of 35 inches of mer- 
cury; the thousandth part of this will be seven two hun- 
dredths of an inch of mercury, and 632 of these parts will 
express the effective portion of the power. By multiplying 
seven two hundredths by 632, we obtain 22 nearly. Now, 
suppose the temperature in the condenser is 1200, the pres- 
sure of steam corresponding to that temperature will be 



296 THE STEAM ENGINE. 

measured by 3^ inches of mercury. Subtracting this from 
22, there will remain 18 T 3 5 inches of mercury, as the effective 
moving force upon the piston; this will be equivalent to 
about 7 lbs. on each circular inch. 

If the- diameter of the piston then be 24 inches, its sur- 
face will consist of a number of circular inches expressed by 
the square of 24, or 24 x 24 = 576 ; and, as upon each of 
these circular inches there is an effective pressure of 7 lbs., 
we shall find the total pressure in pounds by multiplying 
576 by 7, which gives 4032 lbs. 

We shall find the space through which this force works 
per minute, by knowing the length of the cylinder and the 
number of strokes per minute. Suppose the length of the 
cylinder to be 5 feet, and the number of strokes per minute 
21§. In each stroke* the piston will, therefore, move 
through 10 feet, and in one minute it will move through 
215 feet. The moving force, therefore, is 4032 lbs. moved 
through 215 feet per minute, which is equivalent to 215 
times 4032 lbs., or 866,880 lbs., raised one foot per minute. 

For every 33,000 lbs. contained in this, the engine has a 
horse power. To find the horse power, then, of the engine, 
we have only to divide 866,880 by 33,000 ; the quotient is 
26 nearly, and, therefore, the engine is one of 26 horse 
power. 

Let it be required to determine the quantity of water 
which a boiler must evaporate per hour, for each horse power 
of the engine which it works. 

. It has been already explained that one horse power ex- 
presses 33,000' lbs. raised one foot high per minute, or, 
1,980,000 lbs. raised one foot high per hour. The quantity 
of water necessary to produce this mechanical effect by eva- 
poration, will be found by considering that a cubic inch of 
water, being evaporated, will produce a mechanical force 

* By a stroke of the piston is meant its motion from one end of the 
cylinder and back again . 



POWER OF BOILERS. 297 

equivalent to 2160 lbs. raised a foot high. If we divide 
1,980,000, therefore, by 2160, we shall find the number of 
cubic inches of water which must be evaporated per hour, 
in order to produce the mechanical effect expressed by one 
horse power; the result of this division will be 9166, which 
is therefore the number of cubic inches of water per hour, 
whose evaporation is equivalent to one horse power. But 
it has been shown that, for every 6 cubic inches of water 
evaporated in the boiler which are available as a moving 
power, there will be 4 cubic inches intercepted by the en- 
gine. To find, then, the quantity of waste corresponding to 
916 cubic inches of water, it will be necessary to divide that 
number by 6, and to multiply the result by 4: this process 
will give 610 as the number of cubic inches of water wasted. 
The total quantity of water, therefore, which must be evapo- 
rated per hour, to produce the effect of one horse power, will 
be found by adding 610 to 916, which gives 1526. 

This result, however, being calculated upon a supposition 
of a degree of efficiency in the engines which is, perhaps, 
somewhat above their average state, it has been customary 
with engineers to allow a cubic foot of water per hour for 
each horse power, a cubic foot being 1728 cubic inches, or 
above 11 per cent, more than the above estimate. 

(137.) It has been stated, that to evaporate a cubic foot of 
water per hour requires 9 square feet of surface exposed to 
the action of the fire and heated air. This, therefore, is the 
quantify of surface necessary for each horse power, and we 
shall find the total quantity of fire and flue surface necessary 
for a boiler of a given power, by multiplying the number of 
horses in the power by 9; the product will express, in square 
feet, the quantity of boiler surface which must be exposed 
to the fire, one half of this being fire surface and the other 
half flue surface. 

Since the supply of heal to the boiler must be proportion- 
ate to the quantity of fuel maintained in combustion, and the 
quantity of that fuel must depend on the extent of grate 

38 



298 THE STEAM ENGINE. 

surface, it is clear that a determinate proportion must exist 
between the power of the boiler, and the extent of grating 
in the fire place- The quantity of oxygen which combines 
with the fuel varies with the quality of that fuel ; for dif- 
ferent kinds of coal it varies from two to three pounds for 
each pound of coal. 

We shall take it an average of 2§ pounds. Now 0j 
pounds of oxygen will measure 30 cubic feet ; also 5 cubic 
feet of atmospheric air contain 1 cubic foot of oxygen ; and 
consequently 150 cubic feet of atmospheric air will be ne- 
cessary for the combustion of 1 pound of average coals. At 
least one third of the air, which passes through a fire, escapes 
uncombined into the chimney. We must, therefore, allow 
220 cubic feet of atmospheric air to pass through the grate- 
bars for every pound of fuel which is consumed. Now since 
land boilers will consume 15 pounds, and marine boilers 10 
pounds, per hour per horse power, it follows that the spaces 
between the grate bars, and the extent of grate surface, must 
be sufficient to allow 3000 cubic feet of air per hour in land 
boilers, and 2000 cubic feet in marine boilers, to pass through 
them for each horse power, or, what is the same, for each 
foot of water converted into steam per hour. The quantity 
of grate surface necessary for this does not seem to be ascer- 
tained with precision ; but, perhaps, we may take as an ap- 
proximate estimate for land boilers one square foot of grate 
surface per horse power, and for marine boilers two thirds 
of a square foot, the spaces between the grate bars being 
equal to their breadth. 

It is evident that the capacity of a boiler for water and 
steam must have a determinate relation to the power of the 
engine it is intended to supply. For each horse power of 
the engine, it has been shown that a cubic foot of water must 
pass from the boiler in the form of steam per hour. Now, 
it is evident that the steam could not be supplied of a uni- 
form force, if the quantity of steam contained at any mo- 
ment in the boiler were not considerably greater than the 



POWER OP BOILERS. 299 

contents of the cylinder. For example, if the volume of 
steam in the boiler were precisely equal to the capacity of 
the cylinder, then one measure of the cylinder would for 
the moment cause the steam to expand into double its bulk 
and to lose half its force, supposing it to pass freely from the 
boiler to the cylinder. In the same manner, if the volume 
of steam contained in the boiler were twice the contents of 
the cylinder, the steam would for a moment lose a third of 
its force, and so on. It is clear, therefore, that the space al- 
lotted to steam in the boiler must be so many times greater 
than the magnitude of the cylinder, that the abstraction of a 
cylinder full of steam from it shall cause a very trifling di- 
minution of its force. 

In the same manner, we may perceive the necessity of 
maintaining a large proportion between the total quantity of 
water in the boiler, and the quantity supplied in the form of 
steam to the cylinder. If, for example (taking as before an 
extreme case,) the quantity of water in the boiler were only 
equal to the quantity supplied in the form of steam to the 
cylinder in a minute, it would be necessary that the contents 
of the boiler should be replaced by cold water once in each 
minute: and, under such circumstances, it is evident that the 
action of the heat upon the water would be quite unmanage- 
able. But, independent of this, the quantity of water must 
be sufficient to fill the boiler above the point at which the 
flue surface terminates, otherwise the heat of the fuel would 
act upon the part of the boiler containing steam and not wa- 
ter ; and, steam receiving heat sluggishly, the metal of the 
boiler would be gradually destroyed by undue temperature. 

The total quantity of space for water and steam in boilers 
is subject to considerable variation in proportion to their 
power. Small boilers require a greater proportion of steam 
and water room, or a greater capacity of boiler, in proportion, 
than large ones ; and the same applies to their fire surface 
and flue surface. 

The general experience of engineers has led to the conclu- 



300 THE STEAM ENGINE. 

sion, that a low-pressure boiler of the common kind requires 
ten cubic feet of water-room, and ten cubic feet of steam- 
room in the boiler, for every cubic foot which the engine 
consumes per hour, or, what is the same,for each horsepow- 
er of the engine. Thus, an engine of ten-horse power, ac- 
cording to this rule, would require a boiler having the ca- 
pacity of 200 cubic feet, which should be constantly kept 
half filled with water. There are, however, different esti- 
mates of this. Some engineers hoid that a boiler should have 
twenty-five cubic feet of capacity for each horse power of 
the engine, while others reduce the steam so low as eight 
cubic feet. 

In a table of the capacities of boilers of different powers, 
and the feed of water necessary to be maintained in them, 
Mr. Tredgold assigns to a boiler of five-horse power four- 
teen cubic feet of water per horse power ; for one of ten* 
horse power, twelve and a half cubic feet; and, for one of 
forty-horse, eleven cubic feet. 

For engines of greater power it is generally found advan- 
tageous to have two or more boilers of small power, instead 
of one of large power. This method is almost invariably 
adopted on board steam boats, and has the advantage of se- 
curing the continuance of the working of the engine, incase 
of one of the boilers being deranged. It is also found con- 
venient to keep an excess of power in the boilers, above the 
wants of the engine. Thus, an engine of sixty-horse power 
may be advantageously supplied with two forty-horse boil- 
ers, and an engine of eighty-horse power with two fifty- 
horse* boilers, and so on. 

(138.) The pressure of steam in the cylinder of an engine 
is always less than the pressure of steam in the boiler, owing 
to the obstructions which it encounters in its passage through 
the steam pipes and valves. The difference between these 
pressures will depend upon the form and magnitude of the 
passages : the straighter and wider they are, the less the dif- 
ference will be; if they are contracted and subject to bends, 



PROPORTION OF STEAM PIPES. 301 

especially to angular inflexions, the steam will be consider- 
ably diminished in its pressure before it reaches the cylinder. 
The throttle valve placed in the steam pipe may also be so 
managed as to diminish the pressure of steam in the cylin- 
der to any extent : this effect, which is well understood by 
practical engineers, is called wire-drawing the steam. By 
such means it is evidently possible for the steam in the boiler 
to have any degree of high pressure while the engine is 
worked at any degree of low pressure. Since, however, the 
pressure of the steam in the cylinder is a material element 
in the performance of the engine, the magnitude, position, 
and shape of the steam pipe and of the valves are a matter of 
considerable practical importance. But theory furnishes us 
with little more than very general principles to guide us. 
One practical rule which has been adopted is, to make the 
diameter of the steam pipe about one fifth of that of the cy- 
linder : by this means the area of the transverse action of 
the pipe will be one twenty-fifth part of the superficial mag- 
nitude of the piston ; and, since the same quantity of steam 
per minute must flow through this pipe as through the cy- 
linder, it follows that the velocity of the steam, in passing 
through the steam pipe, will be twenty-five times the velo- 
city of the piston. 

(139.) Another rule which has been adopted is, to allow 
a square inch of magnitude, in the section of the steam pipe, 
for each horse power of the engine. 

The result of this and all similar rules is, that the steam 
should always pass through the steam pipe with the same 
velocity, whatever be the power of the engine. 

In engines of the same power, the piston will have very 
different velocities in the cylinder, according to the effective 
pressure of the steam, and the proportions and capacity of 
the cylinder. It is clear from what has been already ex- 
plained, that, when the power is the same, the same actual 
quantity of water, in the form of steam, must pass through 
the cylinder per minute: but, if the steam be used with a 
considerable pressure, being in a condensed state, the same 



302 THE STEAM ENGINE. 

weight of it will occupy a less space; and consequently the 
cylinders of high-pressure engines are smaller than those of 
the same power in low-pressure engines : the magnitude of 
the cylinder and the piston therefore, as* well as the velocity 
of the latter, will depend first upon the pressure of the 
steam. 

But with steam of a given pressure, the velocity of the 
piston will be different: with a given capacity of cylinder, 
and a given pressure of steam, the power of the engine will 
determine the number of strokes per minute. But the ac- 
tual velocity of the piston will depend, in that case, on the 
proportion which the diameter of the cylinder bears to its 
length; the greater the diameter of the piston is with respect 
to its length, the less will be its velocity. In case of sta- 
tionary engines used on land, that proportion of the diame- 
ter of the cylinder to its length is selected, which is thought 
to contribute to the most efficient performance of the ma- 
chine. According to some engineers, the length of the cy- 
linder should be twice its diameter;* others make the length 
equal to two diameters and a half; but there are circum- 
stances in which considerations of practical convenience ren- 
der it necessary to depart from these proportions. In marine 
engines, where great length of cylinder would be inadmissi- 
ble, and where, on the other hand, considerable power is 
required, cylinders of short, stroke and great diameter are 
used. In these engines the length of the stroke is often not 
greater than the diameter of the piston, and sometimes even 
less. 

The actual velocity which has been found to have the best 
practical effect, for the piston in low-pressure engines, is 
about 200 feet per minute. This, however, is subject to 
some variation. 

(140.) A given weight or measure of fuel burnt under the 

* This is the proportion under which the cylinder with a given capa- 
city will present the least possible surface to the cooling 1 effect of the 
atmosphere. 



PROPORTION OP CYLINDER. 303 

boiler of an engine is capable of producing a mechanical ef- 
fect through the means of that engine, which, when express- 
ed in an equivalent number of pounds' weight lifted a foot 
high, is called the duty of the engine. If all the heat de- 
veloped in the combustion of the fuel could be imparted to 
the water in the boiler, and could be rendered instrumental 
in producing its evaporation; and if, besides, the steam thus 
produced could be all rendered mechanically available at the 
working point; then the duty of the engine would be the' 
entire undiminished effect of the heat of combustion; but it 
is evident that this can never practically be the case. In 
the first place, the heat developed by the combustion can 
never be wholly imparled to the water in the boiler: some 
part of it will necessarily escape without reaching the boiler 
at all; another portion will be consumed in heating the 
metal of the boiler, and in supplying the loss by radiation 
from its surface; another portion will be abstracted by the 
various sources of the waste and leakage of steam; another 
portion will be abstracted by the reaction of the condensed 
steam; and another portion of the power will be consumed 
in overcoming the friction and resistance of the engine itself. 
It is apparent that all these sources of waste will vary ac- 
cording to the circumstances and conditions of the machine, 
and according to the form and construction of the furnace, 
flues, boilers, &c. The duty, therefore, of different engines 
will be different; and when such machines are compared, 
with a view to ascertain their economy of fuel, it has been 
found necessary carefully to register and to compare the 
fuel consumed with the weight or resistance overcome. In 
engines applied to manufucturea generally or navigation, it 
is not easy to measure the amount of resistance which the 
engine encounters, but when the engine is applied to the 
pumping of water, its performance is more easily deter- 
mined. 

. In the year 1811, several of the proprietors of the mines 
in Cornwall, suspecting that some of their engines might not 



304 THE STEAM ENGINE. 

be doing a duty adequate to their consumption of fuel, came 
to a determination to establish a uniform method of testing 
the performance of their engines. For this purpose a counter 
was attached to each engine, to register the number of strokes 
of the piston. All the engines were put under the superin- 
tendence of Messrs. Thomas and John Lean, engineers; and 
the different proprietors of the mines, as well as their di- 
recting' engineers, respectively pledged themselves to give 
every facility and assistance in their power for the attain- 
ment of so desirable an end. Messrs. Lean were directed 
to publish a monthly report of the performance of each en- 
gine, specifying the name of the mine, the size of the cylin- 
der, the load upon the engine, the length of the stroke, the 
number of pump lifts, the depth of the lift, the diameter of 
the pumps, the time worked, the consumption of coals, the 
load on the pump, and, finally, the duty of the engine, or 
the number of pounds lifted one foot high by a bushel of 
coals. The publication of these monthty reports commenced 
in August, 1811, and have been regularly continued to the 
present time. 

The favourable effect which these reports have produced 
upon the vigilance of the several engineers, and the emu- 
lation they have excited, both among engine-makers and 
those to whom the working of the machines are intrusted, 
are rendered conspicuous in the improvement which has 
gradually taken place in the performance of the engines, up 
to the present time. In a report published in December, 
1826, the highest duty was that of an engine at Wheal Hope 
mine in Cornwall. By the consumption of one bushel of 
coals, this engine raised 46,838,246 pounds a foot high, or, 
in round numbers, forty-seven millions of pounds. 

In a report published in the^ course of the present year 
(1835) it was announced that a steam engine, erected at a 
copper mine near St. Anstell, in Cornwall, had raised by its 
average work 95 millions of pounds 1 foot high, with a 
bushel of coals. This enormous mechanical effect having 



DUTY OF ENGINES. 305 

given rise to some doubts as to the correctness of the expe- 
riments on which the report was founded, it was agreed that 
another trial should be made in the presence of a number, of 
competent and disinterested witnesses. This trial according- 
ly took place a short time since, and was witnessed by a 
number of the most experienced mining engineers and 
agents : the result was, that for every bushel of coal con- 
sumed under the boiler the engine raised 125J millions of 
pounds weight one foot high. 

(141.) It may not be uninteresting to illustrate the amount 
of mechanical virtue, which is thus proved to reside in coals, 
..in a more familiar manner. 

Since a bushel of coal weighs 84 lbs. and can lift 56,027 
tons a foot high, it follows that a pound of coal would raise 
667 tons the same height ; and that an ounce of cOal would 
raise 42 tons one foot high, or it would raise IS lbs. a mile 
high. 

Since a force of 18 lbs. is capable of drawing 2 tons upon 
a railway, it follows that an ounce of coal possesses mecha- 
nical virtue sufficient to draw 2 tons a mile, or 1 ton 2 miles, 
upon a level railway.* 

The circumference of the earth measures 25,000 miles. If 
it were begirt by an iron railway, a load of one ton would 
be drawn round it in six weeks by the amount of mechani- 
cal power which resides in the third part of a ton of coals. 

The great pyramid of Egypt stands upon a base measur- 
ing 700 feet each way, and is 500 feet high ; its weight be- 
ing 12,760,000,000 lbs. To construct it, cost the labour of 
100,000 men for 20 years. Its materials would be raised 
from the ground to their present position by the combustion 
of 479 tons of coals. 

The weight of metal in the Menai bridge is 4,000,000 lbs., 

* The actual consumption - of coal upon railways is in practice about 
eight ounces per ton per mile. It is, therefore, worked with sixteen 
times less effect than in the engine above-mentioned. 

39 



306 THE STEAM ENGINE. 

and its height above the level of the water is 120 feet : its 
mass might be lifted from the level of the water to its pre- 
sent position by the combustion of 4 bushels of coals.* 

The enormous consumption of coals in the arts and manu- 
factures, and in steam navigation, has of late years excited 
the fears of some persons as to the possibility of the exhaus- 
tion of our mines. These apprehensions, however, may be 
allayed by the assurance received from the highest mining 
and geological authorities, that, estimating the present de- 
mand from our coal mines at 16 millions of tons annually, 
the coal fields of Northumberland and Durham alone are suf- 
ficient to supply it for 1700 years, and after the expiration 
of that time the great coal basin of South Wales will be suf- 
ficient to supply the same demand for 2000 years longer. 

But, in speculations like these, the probable, if not cer- 
tain, progress of improvement and discovery ought not to be 
overlooked; and we may safely pronounce that, long before a 
minute fraction of such a period of time shall have rolled over, 
other and more powerful mechanical agents will altogether su- 
persede the use of coal. Philosophy already directs her finger 
at sources of inexhaustible power in the phenomena of elec- 
tricity and magnetism. The alternate decomposition and re- 
composition of water, by magnetism and electricity, has too 
elose an analogy to the alternate processes of vaporisation 
and condensation, not to occur at once to every mind : the 
developement of the gases from solid matter by the opera- 
tion of the chemical affinities, and their subsequent conden- 
sation into the liquid form, has already been essayed as a 
source of power. In a word, the general state of physical 
science, at the present moment, the vigour, activity, and sa-. 
gacity With which researches in it are prosecuted in every 
civilized country, the increasing consideration in which sci- 

* Some of these examples were given by Sir John Herschel, in his 
Preliminary Discourse on Natural Philosophy ; but since that work was 
written an increased power has been obtained from coals, in the propor- 
tion of 7 to 12f. 



PLAIN RULES FOR RAILWAY SPECULATORS. 307 

entific men are held, and the personal honours and rewards 
which begin to be conferred upon them, all justify the ex- 
pectation that we are on the eve of mechanical discoveries 
still greater than any which have yet appeared; and that the 
steam engine itself, with the gigantic powers conferred upon 
it by the immortal Watt, will dwindle into insignificance in 
comparison with the hidden powers of nature still to be re- 
vealed ; and that the day will come when that machine, 
which is now extending the blessings of civilisation to the 
most remote skirts of the globe, will cease to have existence 
except in the page of history. 



CHAPTER XIX. 



PLAIN RULES FOR RAILWAY SPECULATORS. 

(142.) For some time after the completion of the Liver- 
pool and Manchester railway, doubts were entertained of 
its ultimate success as a commercial speculation ; and, even 
still, after several years' continuance, some persons are 
found, sceptical by temperament, who have not acquired full 
confidence in the permanency of its advantages. The pos- 
sibility of sustaining a system of regular transport upon it, 
with the unheard of speed effected at the commencement of 
the undertaking, was, for a long period, questioned by a 
considerable portion even of the scientific world ; and, after 
that possibility was established, by the regular performance 
of^ some years, the practicability of permanently profitable 
work, at that rate of speed, was still doubted by many, and 
altogether denied by some. The numerous difficulties to be 
encountered, and the enormous expense of locomotive power, 
have been fully admitted by the directors in their semi- 



308 ' •* THE STEAM ENGINE. 

annual reports. Persons interested in canals and other rival 
establishments, and others constitutionally doubtful of every- 
thing, attributed the dividends to the indirect proceedings 
of the managers, and asserted that when they appeared to be 
sharing their profit's, they, in reality, were sharing their 
capital. This delusion, however, could not long continue, 
and the payment of a steady semi-annual dividend of 4J per 
cent, since the opening of the railway, together with the 
commencement of a reserved fund of a considerable amount, 
with a premium of above 100 per cent, on the original 
shares, has brought conviction to understandings impenetra- 
ble to general reasoning; and the tide of opinion, which, 
for a time, had turned against railways, has now, by the 
usual reaction, set in so violently in their favour, that it be- 
comes the duty of those who professionally devote them- 
selves to such inquiries, to restrain and keep within mode- 
rate bounds the public ardour, rather than to stimulate it. 

The projects for'the construction of great lines of internal 
communication which have been announced would require, 
if realized, a very large amount, of capital. Considering 
that the estimated capital is invariably less than the amount 
actually required, we shall not, perhaps, overrate the extent 
of the projected investments if we estimate them at fifty 
millions. The magnitude of this amount has created alarm 
in the minds of some persons, lest a change of. investment 
so extensive should produce a serious commercial shock. 
It should, however, be considered that, even if all the pro- 
jected undertakings. should be ultimately carried into execu- 
tion, a long period must elapse, perhaps not less than fifteen 
or twenty years, before they can be all completed: the capi- 
tal will be required, not suddenly, but by small instalments, 
at distant intervals of time. Even i£ it were true, therefore, 
that, to sustain their enterprises, an equivalent amount of 
capital .must be withdrawn from other investments, the 
transfer would take place by such slow degrees as to create 
oo serious inconvenience. But, in fact, it. is not probable that 



PLAIN RULES FOR RAILWAY SPECULATORS. 309 

any transfer of capital whatever will be necessary. Trade 
and manufacturers are at the present moment in a highly 
flourishing condition ; and the annual accumulation of capital 
in the country is so great, that the difficulty will probably 
be, not to find capital to meet investments, but to find suita- 
ble investments for the increasing capital. In Manchester 
alone, it is said that the annual increment on capital is no 
less than three millions. In fifteen years, therefore, this 
mart alone would be sufficient to supply all the funds neces- 
sary for the completion of all the proposed railroads, without 
withdrawing capital from any other investment. 

The facilities which these Joint Stock Companies offer for 
the investment of capital, even of the smallest amount, the 
temptations which the prospect of large profits hold out, and 
the low interest obtained on national stock of every descrip- 
tion, have attracted a vast body of capitalists, small and 
great, who have subscribed to these undertakings with the 
real intention of investment. But, on the other hand, there 
•is a very extensive bod)'' of speculators who engage in them 
upon a large scale, without the most distant intention, and, 
indeed, without the ability, of paying up the amount of 
their shares. The loss which the latter class of persons 
may sustain would, probably, excite little commiseration, 
were it not for the consequences which must result to the 
former, should a revolution take place, and the market be 
inundated with the shares of these gambling speculators, 
who buy only to sell again. Effects would be produced 
which must be ruinous to a large proportion of the bona fide 
subscribers. It may, therefore, be attended with some advan- 
tage to persons who really intend to make permanent invest- 
mentsof this nature, to state, in succinct and intelligibleterms, 
the principal circumstances on which the efficiency and econo- 
my of railroads depend, so as to enable them, in some measure, 
to form a probable conjecture of the prospective advantages 
which the various projects hold out. In doing this, we 
shall endeavour, as much as possible, to confine our state- 



310 THE STEAM ENGINE. 

merits to simple facts and results, which can neither be de- 
nied nor disputed, leaving, for the most part, the inferences 
to which they lead to be deduced from them by others. 

It may be premised, that persons proposing to engage in 
any railroad speculation should obtain Ji?'st a table of gra- 
dients; that is, an account of all the acclivities upon the 
line from terminus to terminus, stating how many feet in a 
mile each incline rises or falls, and its length. Secondly, 
it would also be advantageous to have a statement of the 
lengths of the radii of the different curves as well as the 
lengths of the curves themselves. Thirdly, an account of 
the actual intercourse which has taken place, for a given 
time, upon the turnpike road connecting the proposed ter- 
mini, stating the number of coaches licensed, and the average 
number of passengers they carry; also as near an account of 
the transport of merchandise as may be obtained. The lat- 
ter, however, is of less moment. An approximate estimate 
may be made of the intercourse in passengers, by allowing 
for each coach, upon each trip, half its licensed complement 
of load. Fourthly, the water communication by canal or 
otherwise between the places; and the amount of tonnage 
transported by it. With the information thus obtained, the 
following succinct maxims will be found useful:-— 



No railroad can be profitably worked without a large inter- 
course of passengers. Goods, merchandise, agricultural pro- 
duce, &c, ought to be regarded as of secondary importance. 

ir. 

A probable estimate of the number of passengers to be 
expected upon a projected line of railroad may be made by 
increasing the average number of passengers for the last 
three years, by the common road, in a twofold proportion. 



PLAIN RULES FOR RAILWAV SPECULATORS. 311 

The average number of passengers daily between Liver- 
pool and Manchester, before the formation of the railway, 
was about 450 ; the present average number; is above 1300. 
A short railroad of about five miles is constructed between 
Dublin and Kingstown : on which the average number of 
passengers daily between those places has increased in near- 
ly the same proportion. 



in. 



Passengers can be profitably transported by canal, at a 
speed not exceeding nine miles an hour, exclusive of delays 
at locks, at the rate of one penny per head per mile. The 
average fares charged upon the Manchester railway are at 
the rate of 1 f £ \^d. per head per mile, the average speed be- 
ing twenty miles an hour. 

To transport passengers at the rate of ten miles an hour 
on a railway, would cost very little less than the greater 
speed of twenty miles an hour, so that a railroad could not 
enter into competition on equal terms with a canal by equal- 
ising the speed. 

The. canal between Kendal and Preston measures 57 
miles : passengers are transported upon it between these 
places at the average speed of a mile in 6| minutes, or 9i 
miles an hour nearly, exclusive of delays at locks. The 
fare charged is at the average rate of a penny a mile. There 
are eight locks, rising 9 feet each,' and a tunnel 400 yards 
long, through which the boat is tracked by hand ; the tunnel 
requires 5 minutes, and the locks from 25 to 2S minutes, in 
descending, and 45 to 4S minutes in ascending. 

Similar boats are worked on the Forth and Clyde, and 
the Union canals in Scotland, and on the Paisley and John- 
stone canal at nearly the same fares. 



312 THE STEAM ENGINE. 



At the fare of 1-^d. per head per mile, the profit on the 
Manchester railroad is 100 per cent, on the disbursements 
for passengers. 



Goods can be profitably transported by canal at a lower 
tonnage than by railroads ; the speed on the canal (for goods) 
being, however, but one-fifth of the speed on the railroad. 



VI. 



Goods are transported on the Liverpool and Manchester 
railroad at three-pence three farthings per ton per mile, with 
a profit of about 40 per cent, upon the disbursement, having 
the competition of a canal between its termini. 



A long railroad can be worked with greater relative eco- 
nomy than a short one. 



VIII. 



Steam engines work with the greatest efficiency and eco- 
nomy, when the resistance they have to overcome is perfect- 
ly uniform and invariable. 



IX. 



The variation of resistance on railroads depends, first, on 
acclivities, secondly, on curves. 

By curves are meant the changes of direction of the road 
to the right or to the left. The direction of a railroad can- 



PLAIN RULES FOR RAILWAY SPECULATORS. 313 

not be changed suddenly by an angle, but must be effected 
gradually by a curve. Supposing the curve to be (as it ge- 
nerally is) the arc of a circle, the radius of the curve is the 
distance of the centre of the circle from the curve. This 
radius is an important element in the estimate of the road. 



The more nearly a railroad approaches to an absolute le- 
vel, and perfect straightness, the more profitably will it be 
worked. 



XI. 



The total amount of mechanical power necessary to trans- 
fer a given load from one extremity of a railroad to another 
is a matter of easy and exact calculation, when the gradients 
and curves are known; and the merits of different lines may 
be compared together in this respect : but it is not the only 
test of their efficiency which must be applied. 



XII. 



A railroad having gradients exceeding seventeen feet in a 
mile will require more mechanical power to work it than it 
would were it level; and the more of these excessive gradi- 
ents there are upon it, and the more steep they are, the 
greater will be this disadvantage. 



XIII. 



Although a railroad having no gradients exceeding seven- 
teen feet in a mile does not require more mechanical power 
than a level, yet the mechanical power which it requires will 
not be so advantageously expended, and, therefore, it will 
not be so economical. 

40 



314 THE STEAM ENGINE. 

xiv. 

A railroad which has gradients above thirty feet in a mile 
will require such gradients to be worked by assistant loco- 
motive engines, which will be attended with a waste of 
power, and an increase of expenditure, more or less, accord- 
ing to the number and length of such gradients. 

xv. 

A very long inclined plane cannot be worked by an as- 
sistant locomotive without a wasteful expense. Gradients 
exceeding seventeen feet per mile must, therefore, be short. 



XVI. 



Gradients exceeding fifty feet in a mile cannot be profit- 
ably worked except by stationary engines and ropes, an ex- 
pedient attended with so many objections as to be scarcely 
compatible with a large intercourse of passengers. 



XVII. 



Steep gradients, provided they descend from the extre- 
mities of a line, are admissible provided they be short. 

It is evident that in this case the inclined planes will help 
at starting to put the trains in motion, at the time when, in 
general, there would be the greatest strain upon the moving 
power ; and, in approaching the terminus, the momentum 
would be sufficient to carry the train to the top of the plane, 
if its length were not great, since it must, at all events, come 
to a stop at the extremity. 

XVIII. 

The effect of gradients in increasing the resistance during 



PLAIN RULES TO RAILWAY SPECULATORS. 315 

the ascent may be estimated by considering that a gradient 
of seventeen feet in a mile doubles the resistance of the le- 
vel, thirty-four feet in a mile triples it, and eight and a half 
feet in a mile adds one half its amount, and so on. 



XIX. 



With the speed now attainable on railways, curves should 
be avoided with radii shorter than a mile. Expedients may 
diminish the resistance, but, through the negligence of en- 
gine drivers, they must always be attended with danger. 
Curves are not objectionable near the extremities of a line. 



xx. 



The worst position for a curve is the foot of an inclined 
plane, because of the velocity which the trains acquire in the 
descent, and the occasional impracticability of checking 
them. 



XXI. 



In proportion as the speed of locomotives is increased by 
the improvements they are likely to receive, the objections 
and dangers incident to curves will be increased. 



XXII. 



The difficulty which attends the use of long tunnels arises 
from the destruction of the vital air which is produced by 
the combustion in the furnaces of the engines. Tunnels on 
a level should, therefore, be from twenty-five to thirty feet 
high, and should be ventilated by shafts or other contriv- 
ances. 



316 THE STEAM ENGINE. 

XXIII. 

The transition from light to darkness, the sensation of hu- 
midity, and the change in summer from a warm atmosphere 
to a coid one, will always form an objection to long tunnels 
on lines of railroad intended for a large intercourse of pas- 
sengers. 



xxiv. 



All the objections to a tunnel are aggravated when it hap- 
pens to be upon an acclivity. The destruction of vital air in 
ascending it will be increased in exactly the same propor- 
tion as the moving power is increased. Thus, if it ascend 
17 feet in a mile, the destruction of vital air will be twice as 
great as on a level; if it ascend 34 feet in a mile, it will be 
three times as great ; 51 feet in a mile, four times as great, 
and so on. 



xxv. 



If by an overruling necessity a tunnel is constructed on 
an acclivity, its magnitude and means of ventilation should 
be greater than on a level, in the same proportion as the re- 
sistance produced by the acclivity is greater than the resist- 
ance upon a level. 

XXVI. 

Tunnels should be ventilated by shafts at intervals of not 
more than 200 yards. 

xxvu. 

While a train is passing through a tunnel, no beneficial ven- 
tilation can be obtained from shafts. The engine will leave 



PLAIN RULES FOR RAILWAY SPECULATORS. 317 

behind it the impure air which it produces, and the passen- 
gers will be enveloped in it before it has time to ascend the 
shafts. Sufficient magnitude, however, may be given to the 
tunnel to prevent any injurious consequences from this cause. 
A disagreeable and inconvenient odour will be experienced. 

XXVIII. 

Tunnels on a level, the length of which do not exceed a 
third of a mile, will probably not be objectionable. Tunnels 
of equal length upon acclivities would be more objection- 
able. 

I may observe generally that we have as yet little or no 
experience of the effect of tunnels on lines of railroad worked 
by locomotive engines, where there is a large intercourse of 
passengers. On the Leicester and Swannington railroad, 
there is a tunnel of about a mile long, on a part of the road 
which is nearly level; it is ventilated by eight shafts, and I 
have frequently passed through it with a locomotive engine. 
Even when shut up in a close carriage the annoyance is 
very great, and such as would never be tolerated on a line 
of road having a large intercourse in passengers. This rail- 
road is chiefly used to take coals from some collieries near 
Swannington, and there is no intercourse in passengers upon 
it, except of the labouring classes from the adjacent villages: 
the engines burn coal, and not coke ; and they consequently 
produce smoke, which is more disagreeable than the gases 
which result from the combustion of coke. This tunnel 
also is of small calibre. 

On the Leeds and Selby railroad there is a tunnel, on a 
part which is nearly level, the length of which is 700 yards, 
width 22 feet, height 17. It is ventilated by three shafts of 
about 10 feet diameter and 60 feet high. There is an inter- 
course of passengers amounting to four hundred per day, 
upon this road, and, generally speaking, they do not object 



318 THE STEAM ENGINE. 

to go through the tunnel with a locomotive engine. The 
fuel is coke. 

(Z) In order to show the present state of railroad trans- 
portation in the United States, and enable our readers to 
compare it with the opinions and facts adduced by Dr. 
Lardner, we take the latest accounts from the Charleston 
and Hamburgh Railroad. The engines drag a train of cars 
which carry a load of 130 tons, and perform the distance 
(240 miles) in three days, travelling only by day-light. 
With these loads they mount planes having inclinations of 
37 feet per mile. The same engines are capable of carrying 
passengers at the rate of 40 miles per hour, and often per- 
form 30, but their average speed is limited by regulation to 
20 miles per hour. 

This railroad is remarkable for being the largest which 
has yet been constructed, and is besides an object of just 
pride, in as much as it was commenced at a time, when ac- 
cording to Dr. Lardner, the subject was but imperfectly 
understood even in Europe, and all its arrangements are due 
to native talent and skill, unassisted by previous discoveries 
in Europe. — a. e. 



INDEX. 



A. 



Atmospheric air, elastic force of, 23 

Atmospheric pressure rendered available as a mechanic agent by 

Denis Papin, 43 

Atmospheric engine, first conception of by Newcomen, 61. Des- 
cription of, 63. Advantage of over that of Savery, 69 

B. 

Barometer, the, 21 

Barometer gauge, the, 123 

Belidor, 133 

Birmingham and London railroad, probable advantages to be derived 

from, 206 

Black, Dr., his doctrine of latent heat, 76 

Blasco de Garay, his contrivance to propel vessels, 42 

Blinkensop, Mr., constructs a locomotive engine, 161 

Boiler, methods for showing the level of water in the, 118. Its 

power and proportions, ~ 297 

Bolton, Matthew, his connexion with Watt, 88 

and Watt, Messrs., immense expenditure of, in bringing 

their engines into use, 91 

Booth, Mr., his method of using tubes to conduct heated air through 
locomotive boilers, 176. His report to the directors of the Liver- 
pool and Manchester railway on the apparent discrepancies of 
Messrs. Walker and Rastrick's estimate of locomotive power, 189 

Braithwaite and Ericsson, Messrs., then* " Novelty" described, 175 

Branca, Giovanni, his machine for propelling a wheel by a blast of 

steam, 45 

Brewster, Dr., 79 

Brunton, Mr., his improved furnace described, 130 



320 INDEX. 



Canals, transport on, 208. Experiments with boats on, 209. Com- 
parison of with railroads, 210 
Cartwright, Rev. Mr., description of his improvements in the steam 

engine, , 142 

Cawley, John, 61 

" Century of Inventions" by the Marquis of Worcester, 46 

Chapman, Messrs., obtain a patent- for working a locomotive by 

means of a chain, 162 

Church, Dr., his steam carriage, 239 

Cohesion, attraction of, 32 

Condensation of solids, 28 

Condensation by jet, accidental discovery of, 65 

Cornwall, reports of duty of steam engines in, 303 

Cotton, processes in the culture of, 18 

Cylinder, its proportions, 300 

D valve, description of the, 113 

Damper, the, 126 

Duty of a steam engine, 291 

Duty, reports of, in Cornwall, 303 

E. 

Eccentric; description of the, 111 

Edelcrantz,the Chevalier, 127" 

F. 

Farey, Mr., his statement respecting the variations in the work of dif- 
ferent steam engines, 133 
Fluids, property of, 21 
Fly-wheel, introduction of the, 104 
Four-way cock, description of the, 115 
Fuel, table of the consumption of, in different locomotives, 180 

G. 

Governor, description of the, 105 

Guericke, Otto, inventor of the air pump, 70 

Gurney, Mr., his steam carriage, 216 



INDEX. 321 

H. 

Hackworth, Mr., description of his engine, the " Sanspareil," 173 
Hall, Mr. Samuel, his patent steam engine, 248. Its advantages for 

navigation, 249. Its successful application, 250 

Hamilton, Duke of, 88 

Hancock, Mr. Walter, his steam carriage, 235 

Heat, phenomena of, 29 

Hero of Alexandria, description of his machine, 41 

Hopper, the, or apparatus for supplying the fireplace with coals, 131 

Hornblower, Mr., his double cylinder engine, 134 

Horse power and steam power, comparison between, 202 

Horsepower of an engine, 291. Method of calculating it, 293 
Howard, Mr. Thomas, his patent steam engine, 253 . Its advantages 

in navigation, 256 

Huskisson, Mr., 154 



Inclined planes, their injurious effects on railroads, 194. Methods 

proposed to remedy these, 194 

India, steam communication with, 271 

K. 

Kendal and Preston canal, speed of boats on, . 209 



Leeds and Selby railroad, * 317 

Leicester and Swannington railroad, .317 

Leupold, his " Theatrum Machinarum," 116. His engine described, 147 
Liquids converted into vapour by the application of heat, 27. Differ- 
ence of temperatures of, 35 
Liverpool and Manchester railroad, effects of the introduction of 
steam transport on, 152." "Want of experience in the construction 
of the engines, 154. Proceedings of the directors, 167. Premium 
offered by them for the best engine, 169. Experiments made 
on, 183. Passengers the chief source of profit to the proprietors, 204 
Liverpool and London, supposed advantages from the connexion of 

these places by railroad, 206 

Llangennech coal, its economy, 267 

Locomotive engines, description of the "Rocket," 171. The "Sans- 
pareil," 173. The "Novelty," 175. Mr. Booth's method of using 
41 



322 INDEX. 

tubes to conduct heated air through boilers, 177. Mr.'Stephen- 
son's method of subdividing the flue, 179. Amount of fuel con- 
sumed in, 180. Progressive improvement of, 180. Description of an 
improved form of engine, 181. Circumstances on which their ef- 
ficiency depends, 183. Experiments with, on Liverpool and Man- 
chester railroad, 184. Defects of, 186. Improvement in the method 
of tubing, 188. Proposed methods for working them on levels and 
inclined planes, 194. Extraordinary speed and power of, 204. 
Their introduction on turnpike roads, 213 

Locomotive power, expense of, 188 

Locomotive boilers, improved form of, 177 

M. 

Machines, definition of, 19 

Manufactures, motions required in, 19 

Morgan, Mr., his patent paddlewheel, 259 

Morland, Sir Samuel, his application of steam to raise water, 47 

Motion, a primary agent in the cultivation of cotton, 18. Variety of, 19 
Murray, Mr., description of his suggested slide valve, 113 

N. 

Newcomen, Thomas, and John Cawley, turn their attention to the 

practicability of applying steam engines to the drainage of mines, 61 

Newcomen, Thomas, his construction of the atmospheric engine, 63 

" Novelty," description of the, 175 



Ogle, Mr., his steam carriage, 239 

Oldham, Mr., his modification of the self-regulating furnace, 132 

P. 

Paddlewheel, the common one, 257. Mr. Morgan's patent one, 259 
Papin, Denis, his contrivance, by which atmospheric pressure is ren- 
dered available as a mechanical agent, 48. Description of his steam 
engine, 71 

Parallel motion, description of the, 95 

Piston, its velocity, 302 

Post-office steam packets, their speed, 268 

Potter, Humphrey* his contrivance for working the valves, 67 

Power of a steam engine, how estimated, 291 



INDEX. 323 

R. 

Railroads, first introduction of locomotives on, 151. Important effects 
to be expected from their adoption, 155. Imaginary difficulty re- 
specting the progression of carriages on, 160. Various methods 
resorted to, to remedy this supposed difficulty, 161. One of these 
methods described, 162. Comparative estimate of the expenses 
of locomotive and stationary engines, 168. Difficulties arising from 
changes of level, 192. Their great extension, 206. Comparison 
of, with turnpike roads, 213. Inclined planes on, 194 

Railway speculators, plain rules for, 307 

Roads, their resistance to draft, 213. Compared with railroads, 213 

Robinson, Dr., 73 

Roebuck, Dr., assistance rendered by him to Watt, 87. His embar- 
rassments, 8 8 
"Rocket," description of the,. 171 



S. 



Savery, Thomas, obtains a patent for an engine to raise water, 49. 
His discovery of the principle of condensation, 49. Constructs the 
first engine, brought into operation, 50. Description of, 51. Inef- 
ficiency of, 57. Great consumption of fuel necessary in his engines; 
60. Different purposes to which he proposed to apply the steam 
engine, 61. Limited power of his engine, 69 

" Sanspareil, description of the, 173 

Smeaton turns his attention to the details of the atmospheric en- 
gines, 73 
Solids converted into liquids by the application of heat, 27 
Solomon De Caus, description of the apparatus of, 43 
Somerset, Edward, Marquis of "Worcester, invention of the steam 
engine ascribed to him, 45. Description of his contrivance, 45. 
Similar to Savery's, 46. His "Century of Inventions," 46 
Steam carriages, Mr. Gurney's, 216. Mr. Hancock's, 235. Mr. Ogle's, 

238. Dr. Church's, 239 

Steam, its properties described, 30. Its mechanical power in propor- 
tion to the water evaporated, 277. Its volume, 279. Its quantity 
of heat, 279. Its power in respect of fuel, 280. Its expansive ac- 
tion, how advantageous, 280. Combination of expansion with con- 
densation, 285. High pressure, its expansive action, 288. Ex- 
amples illustrative of its mechanical force, 305 
Steam engine, first mover in, 19. Physical effects connected with, 
20. Claims to the invention of, 38. Efficacy of, as a mechanical 



324 INDEX. 

agent, 39. First brought into operation by Savery, 50. Its inef- 
ficiency, 58. First proposed to be applied to the drainage of 
mines, 61. Accidental discovery of condensation by jet, 65. Fur- 
ther improvements by Humphrey Potter and Beighton, 67, 68. 
Description of Papin's engine, 71. First experiments of Watt and 
subsequent improvements, 73. Dr. Black's theory of latent heat, 
76. Watt's method of condensation, 76. Further improvements of 
Watt, 77. Description of Watt's single-acting engine, 80. The cold 
water pump, 86. The hot water pump, 86. Erection of a speci- 
men engine at Soho, and gradual demand for them, 89. The sin- 
gle-acting engine inapplicable to manufactures, 91. The double- 
acting engine, 92. Invention of the parallel motion, 95. Introduc- 
tion of the rotatory motion, 100. The fly-wheel, 104. The go- 
vernor, 105. The throttle valve, 105. The eccentric, 111. The 
D valve, 113. The four-way cock, 115. Methods for ascertaining 
the level of water in the boiler, 118. The engine made to feed 
its own boiler, 120. Waste of water prevented, 121. The steam 
gauge, 122. Barometer gauge, 123. The damper, 125. Methods 
proposed for preventing the waste of fuel, 128. Mi*. Brunton's 
furnace described, 130. Mr. Oldham's modification of the self- 
regulating furnace, 132. Improvements by Hornblower and 
Woolf, 134. Description of the improvements of Mr. Cartwright, 
142. High-pressure engines, 145. Leupold's engine described, 
147. Construction of the first high pressure engine by Messrs. . 
Trevithick and Vivian, 148. First application of the steam engine 
to propel carriages on railroads, 151. How applied to navigation, 
242. Marine engine ; its form and arrangement, 243. Mr. How- 
ard's patent engine described, 253. Mr. Hall's engine described, 248 

Steam gauge, the, , 122 

Steam navigation, incredulity which existed respecting, 159. The 
limit of its present powers, 264 

Steam vessels, their average speed, 265. Their average consump- 
tion of fuel, 265. Proportion of their power to their tonnage, 
266. Speed of post-office packets, 268. Iron steam vessels, 269. 
American vessel called the " Cigar Boat," its great speed, 270 

Stephenson's, Mr., description' of an engine constructed by him, 164. 
Premium awarded to this engine by the Liverpool and Manchester 
Railway Directors, 170. His method of dividing the flues, 179 

Stephenson" and Lock, Messrs., appointed by the Directors of the Li- 
verpool and Manchester Railroad to make reports on the merits of 
various railroads, \Qy 

Run and planet wheels, 101 



INDEX. 325 



Thermometer, description of, 24 
Throttle valve, use of, 104 
Traction, force of, on a railroad, 192 
Tredgold, 70 
Trevithick and Vivian, Messrs., construct the first high-pressure en- 
gine used in this country, 148 

U. 

United States, steam communication with, 274 

V. 

Vacuum, production of, by experiment, 37 

Vapour, elastic, force of, 35 

Valves, Watt's method of working the, 109 

W. 

Walker and Rastrick, Messrs., apparent discrepancy of their estima- 
ted expense of locomotive power, 189 

Washborough takes out a patent for Watt's invention of the rotatory 
motion, 100 

Water, sea, injurious to marine boilers, 245. How remedied by 
blowing out, 246 

Watt, James, important discoveries of, 39. His acquaintance with 
Dr. Robinson and first experiments on the steam engine, 73. His 
subsequent improvements, 75. His method of condensation, 76. 
His first introduction of the air pump into the steam engine, 77. 
Further improvements, 78. His difficulties, 78. Description of 
his single-acting engine, 80. His introduction to Dr. Roebuck, 88. 
Erects his first engine on the estate of the Duke of Hamilton, 88. 
After further improvements, obtains a patent for this engine, in 
conjunction with Roebuck, 88. His difficulties owing to Dr. Roe- 
buck's failure, and subsequent connexion with Bolton, 88. Ob- 
tains an extension of his patent, 89. Ingenious invention of, to 
determine the rate of remumeration he should receive, 89. His 
invention of the parallel motion, 95. His method for producing a 
rotatory motion anticipated by Washborough, who takes out a pa- 
tent for it, 101. His contrivance of the governor, 104. His me- 
thod of working the valves, 109. His suggestion of the D valve, 113 

Wood, Mr. Nicholas, 168 

Woolf, Mr., his improvements in the steam engine, 134. Obtains a 
patent for the double cylinder engine, 137 



